Here are some useful RegEx everyone can use... I'll add more with time.

[mattkenefick]

Search Multiple Words

if( preg_match( "/\s+((word1)|(word2))\s+/" , $str ) )
{
   print "Found: " . $str;
}

 

Find word variations

if( preg_match( "/Joh?n(athan)? Johnson/" , $str ) )
{
   print "Found: " . $str;
}

 

Find Similar Words ( finds bat,cat,mat,rat )

if( preg_match( "/\b[bcmr]at\b/" , $str ) )
{
   print "Found: " . $str;
}

 

 

Find lines that begin with...

if( preg_match( "/^Word\b/" , $str ) )
{
   print "Found: " . $str;
}

 

 

 

Lines that END with...

if( preg_match( "/\bword$/" , $str ) )
{
   print "Found: " . $str;
}

 

 

Escape Quotes

$str = $_POST['value'];
return preg_replace( '/(^|(?<!\\\))\"/', '\\\"', $str );

 

 

 

Drop Lines in file

$str = $_POST['value'];
return ereg_replace( ',[[:space:]]*', ',<br />', $str);

 

 

Extract Queries from URLs

if ( ereg( '^[^?]*\?(.*)$', $str, $matches) )
{
    echo "Found: $matches[1]";
}

 

 

Format US Date

$date = $_POST['date'];
$newDate = preg_replace( "/^(\d{1,2})[-\/.]?(\d{1,2})[-\/.]?((?:\d{2}|\d{4}))$/", "$1-$2-$3", $date);
print $newDate;

 

 

Validate Social Security Numbers

$socialNumber = $_POST['value'];
if (preg_match( "/^00[1-9]|0[1-9]\d|[1-5]\d{2}|6[0-5]\d|66[0-5]|66[7-9]|6[7-8]\d|690|7[0-2]\d|73[0-3]|750|76[4-9]|77[0-2])-(?!00)\d{2}-(?!0000)\d{4}$/", $socialNumber) )
return "Its real";

 

 

 

 

If you have any requests, let me know!

[mattkenefick]

That seemed like a lot more that it reads, it takes a while to type them lol. They're so specific that it's easy to make a mistake. I'll add more soon.

[effigy]

There are many things to consider:

 

1. You have parentheses that are not needed and cause the engine to work harder.

2. Not bad, but the lack of word boundaries or whitespace could match more than you'd like.

3. In a rare instance you might encounter a word or variation thereof that uses an apostrophe; this would trigger the word boundary.

4. OK, but keep #3 in mind. If you search for /^Can\b/ you'll find "Can" even though the first word may be "Can't."

5. #3 and #4 still apply, but the chance of this breaking should be much more difficult. Be careful with $ because it's not a true end of line--that's \z.

 

Case insensitivity needs to be considered for all of these as well.

 

That's all the review I have for now...