PHP program to find the longest substring of vowels .
< ? php function isVowel ( $ c ) { return ( $ c == ' a ' $ c == ' e ' $ c == ' i ' $ c == ' o ' $ c == ' u ' ) ; } function longestVowel ( $ s ) { $ count = 0 ; $ res = 0 ; for ( $ i = 0 ; $ i < strlen ( $ s ) ; $ i ++ ) {