PHP: Some important PHP Snippets

PHP have lots of built-in functions, and most developers know many of them. But a few functions are not very well known, but are super useful. In this article, I have compiled little known but really cool PHP functions.

highlight_string()

When displaying PHP code on a website, the highlight_string() function can be really helpful: It outputs or returns a syntax highlighted version of the given PHP code using the colors defined in the built-in syntax highlighter for PHP.

Usage:

<?php
highlight_string('<?php phpinfo(); ?>');
?>

str_word_count()

This handy function takes a string as a parameter and return the count of words, as shown in the example below.

Usage:

?php
$str = "How many words do I have?";
echo str_word_count($str); //Outputs 5
?>

levenshtein()

Ever find the need to determine how different (or similar) two words are? Then levenshtein() is just the function you need. This function can be super useful to track user submitted typos.

Usage:

<?php
$str1 = "carrot";
$str2 = "carrrott";
echo levenshtein($str1, $str2); //Outputs 2
?>

get_defined_vars()

Here is a handy function when debugging: It returns a multidimensional array containing a list of all defined variables, be them environment, server or user-defined variables, within the scope that get_defined_vars() is called.

Usage:

print_r(get_defined_vars());

escapeshellcmd()

escapeshellcmd() escapes any characters in a string that might be used to trick a shell command into executing arbitrary commands. This function should be used to make sure that any data coming from user input is escaped before this data is passed to the exec() or system() functions, or to the backtick operator.

Usage:

<?php
$command = './configure '.$_POST['configure_options'];

$escaped_command = escapeshellcmd($command);
 
system($escaped_command);
?>

checkdate()

Checks the validity of the date formed by the arguments. A date is considered valid if each parameter is properly defined. Pretty useful to test is a date submitted by an user is valid.

Usage:

<?php
var_dump(checkdate(12, 31, 2000));
var_dump(checkdate(2, 29, 2001));

//Output
//bool(true)
//bool(false)
?>

php_strip_whitespace()

Returns the PHP source code in filename with PHP comments and whitespace removed. This is similar to using php -w from the commandline.

Usage:

<?php
// PHP comment here

/*
 * Another PHP comment
 */

echo        php_strip_whitespace(__FILE__);
// Newlines are considered whitespace, and are removed too:
do_nothing();
?>

The output:

<?php
 echo php_strip_whitespace(__FILE__); do_nothing(); ?

popen in PHP

popen — Opens process file pointer
Syntax:

resource popen ( string $command , string $mode )
Opens a pipe to a process executed by forking the command given by command.

Parameters:

command
The command

mode
The mode

Return values: Returns a file pointer identical to that returned by fopen(), except that it is unidirectional (may only be used for reading or writing) and must be closed with pclose(). This pointer may be used with fgets(), fgetss(), and fwrite(). When the mode is 'r', the returned file pointer equals to the STDOUT of the command, when the mode is 'w', the returned file pointer equals to the STDIN of the command.

If an error occurs, returns FALSE.



Example #1 popen() example

<?php
$handle = popen("/bin/ls", "r");
?>
If the command to be executed could not be found, a valid resource is returned. This may seem odd, but makes sense; it allows you to access any error message returned by the shell:

Example #2 popen() example

<?php
error_reporting(E_ALL);

/* Add redirection so we can get stderr. */
$handle = popen('/path/to/executable 2>&1', 'r');
echo "'$handle'; " . gettype($handle) . "\n";
$read = fread($handle, 2096);
echo $read;
pclose($handle);
?>


Note:
If you're looking for bi-directional support (two-way), use proc_open().
Note: When safe mode is enabled, you can only execute files within the safe_mode_exec_dir. For practical reasons, it is currently not allowed to have .. components in the path to the executable.
Warning
With safe mode enabled, the command string is escaped with escapeshellcmd(). Thus, echo y | echo x becomes echo y \| echo x.