preg_replace with overlapping parameters

Question

Im trying to right a script that divides vowels and suffixes with a hyphen.

<?php
$string = 'celebrationing';
$patterns = array();
$patterns[0] = '/a/';
$patterns[1] = '/e/';
$patterns[2] = '/i/';
$patterns[3] = '/o/';
$patterns[4] = '/u/';
$patterns[5] = '/tion/';

$replacements = array();
$replacements[0] = '-a';
$replacements[1] = '-e';
$replacements[2] = '-i';
$replacements[3] = '-o';
$replacements[4] = '-u';
$replacements[5] = '-tion';

echo preg_replace($patterns, $replacements, $string);


?>

The script works fine for vowels, but when i comes to the suffix -tion, it isnt printing the hyphen.

Output: c-el-ebr-at-i-on-ing

What im thinking is the fact that both -i and -o are vowels is whats messing the whole process up.

How do I allow all six patterns to be recognized, with all instances of -tion superceding -i and -o?

Jerry · Accepted Answer · 2013-10-28 18:34:32Z

6

You can use a simpler regex:

preg_replace('/tion|[aeiou]/', "-$0", $string);

regex101 demo

The regex first tries to match tion which thus prevents the matching of i and o later on in the same match.

answered Oct 28, 2013 at 18:34

Jerry

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1 Comment

Thelson Richardson Over a year ago

This is better than what I was thinking! Thanks Jerry!!

Nir Alfasi · Accepted Answer · 2013-10-28 18:41:24Z

2

Not as elegant as Jerry's solution, this one uses negative-lookahead & lookbehind:

<?php

$string = 'celebrationing';
$patterns = array();
$patterns[0] = '/a/';
$patterns[1] = '/e/';
$patterns[2] = '/i(?!on)/';
$patterns[3] = '/o(?<!ti)(?!n)/';
$patterns[4] = '/u/';
$patterns[5] = '/tion/';

$replacements = array();
$replacements[0] = '-a';
$replacements[1] = '-e';
$replacements[2] = '-i';
$replacements[3] = '-o';
$replacements[4] = '-u';
$replacements[5] = '-tion';

echo preg_replace($patterns, $replacements, $string);

OUPUT:

c-el-ebr-a-tion-ing

answered Oct 28, 2013 at 18:41

Nir Alfasi

53.6k12 gold badges94 silver badges138 bronze badges

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