--TEST-- Test preg_replace() function : basic functionality --FILE-- ', 'This shouldn\'t work', $string)); //tries to find '- This is a string' at the end of a string but can't so replaces nothing and prints the unchanged $string. var_dump(preg_replace('<[0-35-9]>', '4', $string)); //finds any number that's not 4 and replaces it with a 4 ('444444444') var_dump(preg_replace('<\b[hH]\w{2,4}>', 'Bonjour', $string)); //finds h or H at the beginning of a word followed by 2-4 characters and replaces it with Bonjour (i.e. Hello -> Bonjour) (was finding the 'his' in This and replacing it) var_dump(preg_replace('<(\w)\s*-\s*(\w)>', '\\1. \\2', $string)); //finds dashes with an indefinite amount of whitespace around them and replaces them with a full stop precedeby no spaces and followed by one space var_dump(preg_replace('<(^[a-z]\w+)@(\w+)\.(\w+)\.([a-z]{2,}$)>', '\\1 at \\2 dot \\3 dot \\4', 'josmessa@uk.ibm.com')); //finds the e-mail address and replaces the @ and . with "at" and "dot" (uses backreferences) ('josmessa at uk dot ibm dot com') ?> --EXPECT-- string(54) "123456789 - Hello, world - This is a string." string(54) "123456789 - Hello, world - This is a string." string(54) "444444444 - Hello, world - This is a string." string(56) "123456789 - Bonjour, world - This is a string." string(42) "123456789. Hello, world. This is a string." string(30) "josmessa at uk dot ibm dot com"