A Beautiful Blog » Regular Expressions

RegexPal: Develop and Test Your Regular Expressions From Your Browser

Cory LaViska — Sat, 14 Mar 2009 20:50:03 +0000

RegexPal is an online regular expression tester build using JavaScript. As you build your pattern, RegexPal offers real-time syntax highlighting, backwards/forwards context awareness, and the ability to match the part of the string that the regex pattern doesn’t match. It’s also really fast.

PHP Functions to Get and Remove the File Extension from a String

Cory LaViska — Thu, 12 Mar 2009 00:52:22 +0000

I use these regular expressions all the time, but it’s much more convenient to have them both in convenient PHP functions.

file_ext()

Returns only the file extension (without the period).

function file_ext($filename) {
	if( !preg_match('/\./', $filename) ) return '';
	return preg_replace('/^.*\./', '', $filename);
}

file_ext_strip()

Returns the file name, less the extension.

function file_ext_strip($filename){
    return preg_replace('/\.[^.]*$/', '', $filename);
}

Validating File Extensions using PHP

Cory LaViska — Wed, 07 Nov 2007 19:39:44 +0000

A PHP function for validating file extensions.

check_extension()

Takes a string filename and checks it for a valid extension provided in $allowed.

Parameters

Argument	Type	Explanation
`$filename`	String	The filename (with or without path) to be checked
`$allowed`	String/Array	A string or array containing the list of extensions that are acceptable
`$case_sensitive`	Boolean	Determines whether or not file extensions are matched in a case sensitive manner (default = false)

Return Values

Returns true if allowed, false otherwise.

Code

function check_extension($filename, $allowed = array(), $case_sensitive = false) {
    // Make sure $allowed is always an array
    if( !is_array($allowed) ) $allowed = array($allowed);

    // Determine file extension
    $file_ext = preg_replace('/^.*\./', '', $filename);

    // Handle case sensitivity
    if( !$case_sensitive ) {
        // Convert all allowed to lowercase
        foreach( array_keys($allowed) as $key ) {
            $allowed[$key] = strtolower($allowed[$key]);
        }
        // Convert file extension
        $file_ext = strtolower($file_ext);
    }

    // Check for match
    if( in_array( $file_ext, $allowed ) ) return true; else return false;
}

Example

Find and Replace Hyperlinks and Email Addresses in PHP

Cory LaViska — Tue, 15 May 2007 00:37:27 +0000

These two PHP functions use regular expressions to add the appropriate HTML anchor tags around hyperlinks and email addresses in $string.

PHP Code

function parseHyperlinks($string) {
    // Add  tags around all hyperlinks in $string
    return ereg_replace("[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]", "\\0", $string);
}

function parseEmails($string) {
    // Add  tags around all email addresses in $string
    return ereg_replace("[_A-Za-z0-9-]+(\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\.[A-Za-z0-9-]+)*(\.[A-Za-z]{2,3})", "\\0", $string);
}

Output

Using parseHyperlinks(), http://domain.com/index.htm becomes:

http://domain.com/index.htm

And using parseEmails(), email@domain.com becomes:

email@domain.com>