php tips & hints

(Automatically generated from php.txt--try the plain text version if any of this looks funny.)

$Id: php.txt 1874 2008-06-12 21:47:36Z mjs $

HOWTO: Install

OS X 10.5 (Leopard):

Install, via port, libxml2, libxslt, libiconv, gd2, freetype, sqlite3.

Once these are installed, configure with (adjust as appropriate if ports are not installed into /Ports):

$ ./configure --prefix=$HOME/workspace/beebo/php \
  --enable-fastcgi --with-xsl=/Ports --with-libxml-dir=/Ports \
  --with-gd=/Ports --with-jpeg-dir=/Ports --with-pdo-sqlite=/Ports \
  --without-sqlite  --with-freetype-dir=/Ports --with-ttf=/Ports \
  --enable-calendar --with-zlib=/Ports --with-iconv --with-openssl \
  --enable-discard-path --with-mysql=$LOCAL --with-pdo-mysql=$LOCAL

$LOCAL is where the MySQL libraries and header files are installed. (e.g. /usr--you can't install MySQL into separate "binary" and "shared" directories.)

You may want to add --without-pear if PEAR is installed separately and/or this build doesn't require it.

You can also drop the --without-sqlite to use the bundled sqlite3. (In this case you also don't need to install sqlite3 via port.)

The directory specified by --prefix determines where PHP is installed. The php and php-cgi binaries can be safely moved to other locations, however a few scripts have this location hardcoded, and won't work if the binaries are moved (phpize, pear).

I don't know exactly what --enable-discard-path does, but it supposedly eliminates a security problem.

(If compiling with <= 10.5.1, replace /usr/include/iconv.h with MacPorts' version before configuring.)

$ make

$ make install

Link php-cgi.dSYM to php-cgi, and php.dSYM to php (DON'T FORGET THIS!) and strip the binaries.

Then, in your .htaccess or httpd.conf file, arrange for .php files to be run through the php-cgi via FastCGI:

 AddHandler fastcgi-script fcgi

 Action application/php-fastcgi /bin/boom.fcgi

 AddType application/php-fastcgi .php

Where /bin/boom.fcgi (bin is a subdirectory of document root, not the filesystem root!) is:

PHP=/Users/mjs/local/php/bin/php-cgi
INCLUDE_PATH=`pwd -L`/../../lib
PHPINI=`pwd -L`/../../etc/php.ini

exec $PHP -c $PHPINI -d include_path=$INCLUDE_PATH

Ubuntu/Debian:

Install the likely module suspects--libxml2, libxslt, etc.--then configure with:

$ ./configure --prefix=$HOME/beebo.org/php \
  --enable-fastcgi --with-xsl=/usr --with-libxml-dir=/usr \
  --with-gd --with-pdo-sqlite=/usr --without-sqlite \
  --with-freetype-dir=/usr --with-ttf=/usr --enable-calendar \
  --with-zlib --with-iconv --with-openssl --enable-discard-path \
  --with-jpeg-dir=/usr/lib --with-png-dir=/usr/lib --with-mysql \
  --with-pdo-mysql

You may want to add --without-pear if PEAR is installed separately and/or this build doesn't require it.

Note that for some reason the JPEG and PNG directory parameters specify the location of their respective libraries, not the root. (I don't know why either of these is necessary; for some reason the bundled GD doesn't come with JPEG and PNG libraries.)

strip the binaries.

SunOS:

Install libxml2, libxslt, gd, libjpeg, libpng, zlib (configure zlib with --shared, otherwise you'll get link errors), then:

$ lconfigure --with-apxs2=$LOCAL/bin/apxs \
  --with-xsl=$LOCAL --with-libxml-dir=$LOCAL --with-gd=$LOCAL \
  --with-jpeg-dir=$LOCAL --with-png-dir=$LOCAL --with-zlib-dir=$LOCAL \
  --enable-debug --with-mysql=/usr/local/mysql --enable-calendar

(Might also need to ln -s $HOME/local/include to $LOCAL/include--one of the dependencies couldn't find the include files from the architecture-independent directory.)

Dreamhost:

Install libxml2, libxslt, then:

$ lconfigure --enable-fastcgi --with-xsl=$LOCAL \
  --with-libxml-dir=$LOCAL --with-gd --with-ttf=/usr \
  --with-freetype-dir=/usr --enable-calendar

(Uses their gd, ttf, freetype, etc.)

To install:

$ make install

Stripping the binary will save a lot of memory (optional):

$ strip `which php`

Note that this doesn't install the full command-line version (cli). To get that you need to

$ make install-cli

however the command-line version has the same filename--this installs a new "php" binary over the top of your old one. (? I think this changed around 5.2.3.)

To get Dreamhost's Apache to run your php under FastCGI, you need these lines in your .htaccess:

# Remove the default action for *.php files.

RemoveHandler php

# For some reason the following really does need to be called
# dispatch.fcgi.  The contents of dispatch.fcgi:
#
#   #!/usr/bin/env bash
#
#   exec ./php
#
# DOCUMENT_ROOT/cgi is symlinked to $LOCAL/bin.  Dreamhost's config
# seems to have already configured fastcgi-script for *.fcgi.

Action php-fastcgi /cgi/dispatch.fcgi
AddType php-fastcgi html
AddType php-fastcgi php

Windows/win32:

Get Apache running first.
Download the "ZIP package".
Add something like the following to httpd.conf:

LoadModule php5module "C:/server/php-5.2.4/php5apache22.dll" PHPIniDir "c:/server/php-5.2.4"
(Probably:) Copy php.ini-recommended to php.ini, and tweak as required. (If enabling modules, be sure to set extension_dir!)
Add your PHP directory to PATH, so that various supporting DLLs (e.g. libmysql.dll, libeay32.dll) can be loaded automatically. (How to modify the PATH.)
(optional) Install the Zend debugger

i. Download site. (The "cygwin_nt-i386" version works fine with the regular Windows binaries.)

i. Put the ZendDebugger.dll from the 52x_comp (thread-safe) directory into your PHP extensions directory. (Probably C:\server\php-5.2.4\ext.)

i. Modify php.ini, as described in the README.txt.

i. Restart Apache. A phpinfo() call should mention the debugger.

i. (After all this, couldn't get breakpoints working.)
(optional) Install the Xdebug debugger

i. Download site.

i. Put the php_xdebug-2.0.0-5.2.2.dll into the PHP extensions directory. (Probably C:\server\php-5.2.4\ext.)

i. Add the following to php.ini:
```
zend_extension_ts=c:/server/php-5.2.4/ext/php_xdebug-2.0.0-5.2.2.dll
xdebug.remote_enable = On
xdebug.remote_host=10.171.99.124
```
i. Restart Apache. A phpinfo() call should mention the debugger.

i. More info

HOWTO: Handle standard input and output

http://php.net/wrappers.php

TIP: Predefined variables

http://php.net/reserved.variables

TIP: Object oriented programing/inheritance

http://php.net/extends

TIP: String concatenation/string operators

Use "." for concatenation; see the PHP manual for more.

HOWTO: Break out of a loop

Use "break".

TIP: Documentation of control structures

http://php.net/manual/en/language.control-structures.php

Includes the alternative syntax.

TIP: Regular expression example

if (!preg_match("/^foo/", "some string")) {
    # ...
}

GOTCHA: ODBC

This doesn't work in PHP:

$sth = odbc_prepare($dbh, $sql);

foreach (...) {
    $res = odbc_execute($sth, $arg);
    ...
}

(The prepared statement gets mashed somewhere--move the odbc_prepare() into the loop...)

GOTCHA: MDB2's SQLite supports SQLite2, not SQLite3!

True! You need to use PDO.

HOWTO: Set the include path from the command line

i.e. the equivalent of PERL5LIB, PYTHONPATH, RUBYLIB, etc.:

$ php -d include_path=$PHPLIB

HOWTO: Create a static constructor

This doesn't seem to be possible in PHP; the best way is to do something like:

Foo::$bar = "hullo, world"!;

class Foo {

  public static $bar;

}

HOWTO: Static (class) variables

class Foo {

  static $bar = null;

  function quux() {
    return self::$bar;
  }

}

HOWTO: Retrieve multiple values/process checkboxes, and multiple selects

Give the variable a name that ends in "[]". If there are multiple keys with the same value, and the keys end in "[]", PHP creates an array of values for that value. i.e. if the HTML looks like

<select multiple name="beer[]">
  <option value="warthog">Warthog</option>
  <option value="guinness">Guinness</option>
  <option value="stuttgarter">Stuttgarter</option>
</select>

and the user selects multiple beers, then

gettype($_REQUEST["beer"]) == "array"

See:

http://www.php.net/variables.external

HOWTO: "apply the PHP way

Use call_user_func_array():

call_user_func_array("foo", array(1, 2, 3));

Note that this can also be used to call a method:

call_user_func_array(array($obj, $method), array(1, 2, 3));

HOWTO: Create MySQL-compatible date string format

date("Y-m-d H:i:s")

HOWTO: Convert XHTML entities to XML

If you need to convert e.g. ’ to ’ do something like:

$table = array(
  '&Aacute;' => '&#193;',
  '&aacute;' => '&#225;',
  ...
);

$s = strtr($s, $table);

See:

http://svn.wikimedia.org/svnroot/mediawiki/tags/REL1_9_3/phase3/includes/Sanitizer.php

for the entity conversion table.

TIP: Error control operator (@)

See:

http://uk3.php.net/manual/en/language.operators.errorcontrol.php

Note that you can prefix method calls with "@" also:

$res = @$doc->loadXML($string);

HOWTO: Convert a UTF-8/Unicode string to XML/HTML entities

I can't figure out how to do this! The closest I can get to is:

$utf32 = iconv("UTF-8", "UTF-32BE", $utf8);

foreach (unpack("N*", $utf32) as $c) {
    $xml .= sprintf("&#%d;", $c);
}

which produces a string where every character is expressed as a numeric entity.

GOTCHA: `error_log()` quotes backlashes

echo("\\hello\\") -> \hello\

error_log("\\hello\\") -> \\hello\\

WART:

odbc_execute($sth, $a);

If any of the element of $a begin and end with a single quote, the bit in between is interpreted as a filename, the contents of which are inserted.

WART:

Very strange arguments in php.ini:

; Define the probability that the 'garbage collection' process is started
; on every session initialization.
; The probability is calculated by using gc_probability/gc_divisor,
; e.g. 1/100 means there is a 1% chance that the GC process starts
; on each request.

session.gc_probability = 1
session.gc_divisor     = 1000

WART:

Include is a "special language construct", which means that these two things are not equivalent:

if ($condition)
  include $this;
else
  include $that;

and

 if ($condition) {
   include $this;
 } else {
   include $that;
 }

WART:

array_filter() and array_map() take their arguments in opposite order:

array array_filter ( array input [, callback callback] )
array array_map ( callback callback, array arr1 [, array ...] )

WART:

imageepsbbox returns an array of four values giving the bottom left and top right coordinates of a given string.

imagettfbbox returns an array of eight values, giving the coordinates of all four corners of a given string.

WART:

parse_str() parses--guess what?--a query string. (Also, the inverse is http_build_query().)

More unfortunately-named pairs:

htmlspecialchars()/htmlspecialchars_decode()
htmlentities()/html_entity_decode()

WART:

The insanity of:

isset($foo)
empty($foo)
is_null($foo)
$foo

(Could possibly add array_key_exists() and defined() to this list too.)

Note also that empty(trim($foo)) doesn't work--the argument to empty() needs to be a variable, not an expression.

WART:

include() is relative to the original file, not the included file.

See:

http://bugs.php.net/bug.php?id=9673

You can include() relative to the included file with:

include(dirname(__FILENAME__) . "/../$filename");

HOWTO: Interpolate complex array/object references

Like this:

echo "This works: {$obj->values[3]->name}";

See:

http://php.net/manual/en/language.types.string.php#language.types.string.parsing.complex

FAQ: How to call parent constructor

parent::__construct(...);

See:

http://php.net/language.oop5.decon

FAQ: How to use a custom statement class with PDO?

This comment describes how to extend PDOStatement:

http://php.net/manual/en/ref.pdo.php#73568

(Not tested.)

FAQ: Why does addition/subtraction not work! (Operator precedence)

The operators "+", "-" and "." have the same precedence. This means that e.g.

error_log("elapsed time = " . $t1 - $t0)

doesn't do what you expect--it evaluates as

error_log(("elapsed time = " . $t1) - $t0)

(This is the same as Perl.)

(The full operator precedence table. Note the Perl-like low precedence "and", "xor", "or".)

GOTCHA: `parse_ini_file()` returns unexpected results

"true", "on", "yes", "1" are converted to "1" (the number 1, as a string).

"false", "off", "no" are converted to "" (the empty string).

"0" is not converted, and is returned as "0" (the number 0, as a string).

Because of this behaviour, and the way values are compared, when checking for a boolean value via parse_ini_file() (i.e. whether some setting is true or false), you should simply use if ($value) { ... } instead of trying to be clever with if ($value == true) { ... }, etc.

(PHP type comparison tables.)

GOTCHA: Array iterators pass by value, not reference

$data = array(array(), array());

print_r($data);

foreach ($data as $d) {
    $d[0] = "qqq";
}

print_r($data);

GOTCHA: Arithmetic comparison: `0.0 !== 0`

0.0 == 0, but 0.0 !== 0. For some reason this isn't listed in the type comparison table.

HOWTO: Pretty-print an array

print_r(), var_export() and the like output a line per key => value pair. If you want a few key => value pairs per line, try something like the following ($table is the original array):

  $a = array();

  foreach ($table as $k => $v) {
    $a[] = sprintf("%11s => %9s,", "'{$k}'", "'{$v}'");
  }

  for ($i = 0; $i < count($a); $i++) {
    echo $a[$i], " ";
    if (($i + 1) % 5 === 0) {
      echo "\n";
    }
  }

(Quick hack, doesn't handle ' in either the key or value, for example.)

HOWTO: Extend PDO and use `__call()` within functions

This doesn't work, and is a bug, at least as of PHP 5.2.5.

It can be fixed by applying a patch and re-compiling.

ERROR: Install fails with libgcrypt error

This happens if you're building with XSL (--with-xsl) and libgcrypt isn't available. You need to install both libgcrypt and its dependency libgpg-error:

ftp://ftp.gnupg.org/gcrypt/libgpg-error ftp://ftp.gnupg.org/gcrypt/libgcrypt

(Or add --without-xsl to your ./configure line.)

ERROR: "Unable to load dynamic library XXX"

(Followed by "The specified module could not be found", and where XXX actually exists.)

PHP seems to produce this error fairly indiscriminately if the module can't be loaded for any reason at all, not just in the case where the module doesn't exist on the filesystem. For example, it can happen if you neglect to include a dependency of XXX, for example loading php_pdo_oci.dll without loading php_pdo.dll.

It can also happen if an external dependency can't be found (database DLLs?) or the wrong version is being found (Apache DLLs? Windows DLLs?). (The PATH is searched for DLLs, but DLLs can come from other places as well, such as Apache's bin directory.)

If you're having trouble with php_mysql.dll, make sure that libmySQL.dll can be found.

If you're having trouble with php_pdo_oci.dll, make sure the Oracle client libraries can be found.

If you're having trouble with php_openssl.dll, make sure libeay32.dll can be found, and that the wrong version (Apache's?) isn't being found.

FAQ: What's the syntax for PDO DSNs?

MySQL
Oracle
Other databases - load the PDO documentation, select the driver you want, the select the "next" page using the navigation at the top or bottom.

HOWTO: `eval()` a string as if it were a PHP file

i.e. a function like include_string($string) to parallel include($filename).

eval($string) evaluates $string as if it were PHP code. If you want to eval a string that looks like a PHP file (i.e. a string that contains '<[QMARK]php' and '[QMARK]>'), do:

function include_string($string) {
  eval('?>' . $string . '<?php ');
}

(Astonishing that this works. What is the parser/interpreter doing there?!)

This is documented, somewhat misleadingly, on the eval manpage.

ERROR: "MDB2 Error: unknown error"

This less than helpful message may be emitted if a pragma command fails. (You do get slightly more helpful error messages if there's an error in your SQL proper.) For example, this error will be emitted if you set the charset to a character set that doesn't exist. To diagnose the problem, it might help to do a var_dump() on the database handle or statement handle--sometimes useful information is embedded there.

HOWTO: Upload large files

Despite appearances, the largest file you can upload is affected by several php.ini settings:

upload_max_filesize
post_max_size
memory_limit (possibly)

It's possible that since the uploaded file needs to be encoded, which increases their size, these limits need to be larger than you think.

TIP: Information about the FastCGI version of PHP

See sapi/cgi/README.FastCGI in the source.

HOWTO: Serialize a DOMNode or DOMElement to a string

Use the saveXML() method on the associated document:

echo $doc->saveXML($node);

FAQ: Where's the inverse of `strftime`?

As far as I can tell, there isn't one. strtotime, date_parse or--if you're using WordPress--mysql2date might do in some circumstances.

HOWTO: Access raw POST data

Use php://input:

$data = file_get_contents("php://input");

The POSTed data is URL-encoded, so you may need to decode it first:

$data = urldecode(file_get_contents("php://input"));

Back

php tips & hints

HOWTO: Install

OS X 10.5 (Leopard):

Ubuntu/Debian:

SunOS:

Dreamhost:

Windows/win32:

HOWTO: Handle standard input and output

TIP: Predefined variables

TIP: Object oriented programing/inheritance

TIP: String concatenation/string operators

HOWTO: Break out of a loop

TIP: Documentation of control structures

TIP: Regular expression example

GOTCHA: ODBC

GOTCHA: MDB2's SQLite supports SQLite2, not SQLite3!

HOWTO: Set the include path from the command line

HOWTO: Create a static constructor

HOWTO: Static (class) variables

HOWTO: Retrieve multiple values/process checkboxes, and multiple selects

HOWTO: "apply the PHP way

HOWTO: Create MySQL-compatible date string format

HOWTO: Convert XHTML entities to XML

TIP: Error control operator (@)

HOWTO: Convert a UTF-8/Unicode string to XML/HTML entities

GOTCHA: error_log() quotes backlashes

WART:

WART:

WART:

WART:

WART:

WART:

WART:

WART:

HOWTO: Interpolate complex array/object references

FAQ: How to use a custom statement class with PDO?

FAQ: Why does addition/subtraction not work! (Operator precedence)

GOTCHA: parse_ini_file() returns unexpected results

GOTCHA: Array iterators pass by value, not reference

GOTCHA: Arithmetic comparison: 0.0 !== 0

HOWTO: Pretty-print an array

HOWTO: Extend PDO and use __call() within functions

ERROR: Install fails with libgcrypt error

ERROR: "Unable to load dynamic library XXX"

FAQ: What's the syntax for PDO DSNs?

HOWTO: eval() a string as if it were a PHP file

ERROR: "MDB2 Error: unknown error"

HOWTO: Upload large files

TIP: Information about the FastCGI version of PHP

HOWTO: Serialize a DOMNode or DOMElement to a string

FAQ: Where's the inverse of strftime?

HOWTO: Access raw POST data

GOTCHA: `error_log()` quotes backlashes

GOTCHA: `parse_ini_file()` returns unexpected results

GOTCHA: Arithmetic comparison: `0.0 !== 0`

HOWTO: Extend PDO and use `__call()` within functions

HOWTO: `eval()` a string as if it were a PHP file

FAQ: Where's the inverse of `strftime`?