These aren’t default functions but I thought I’d post them:
<?php function toalphanum( $string ) { $newstring = ""; for( $i = 0; $i < strlen( $string ); $i++ ) { if( ( ( $string[$i] >= "A" ) && ( $string[$i] < = "z" ) ) || ( ( $string[$i] >= "0" ) && ( $string[$i] < = "9" ) ) ) { $newstring[$i] = $string[$i]; } else { $newstring[$i] = "_"; } // end if } // end for return implode( "", $newstring ); } // end toalphanum function toalpha( $string ) { $newstring = ""; for( $i = 0; $i < strlen( $string ); $i++ ) { if( ( $string[$i] >= "A" ) && ( $string[$i] < = "z" ) ) { $newstring[$i] = $string[$i]; } else { $newstring[$i] = "_"; } // end if } // end for return implode( "", $newstring ); } // end toalpha ?>
Nothing brilliant but I find it useful all over the place.