PHP5.5/PHP5.3 にて、連想配列とSwitchのパフォーマンス比較。結果的にはswitchの方が速く、PHP55の方が速いですよっと。

PHP53.log

$ /usr/local/Cellar/php53/5.3.27/bin/php switch_or_array.php
start arr ... Finish: 10.038110971451
start sw ... Finish: 6.0564711093903

PHP55.log

$ /usr/local/Cellar/php55/5.5.4/bin/php switch_or_array.php
start arr ... Finish: 8.5129861831665
start sw ... Finish: 5.0694410800934

switch_or_array.php

<?php

/** Switch と Array どっちが速いかﾌｧｲ！！  */

function sw ($data) {
  switch ($data) {
		case 'aa': return 1;
		case 'bb': return 2;
		case 'cc': return 3;
		case 'dd': return 3;
		case 'ee': return 3;
		case 'ff': return 3;
		case 'gg': return 3;
		case 'hh': return 3;
		case 'ii': return 3;
		case 'jj': return 3;
		case 'kk': return 3;
		case 'll': return 3;
		case 'mm': return 3;
		case 'nn': return 3;
		case 'oo': return 3;
		case 'pp': return 3;
		case 'qq': return 3;
		case 'rr': return 3;
		case 'ss': return 3;
		case 'tt': return 3;
		case 'uu': return 3;
		case 'vv': return 3;
		case 'ww': return 3;
		case 'xx': return 3;
		case 'yy': return 3;
		case 'zz': return 3;
	}
}

function arr ($data) {
	$arr = array( 
		 'aa'=>  3,
		 'bb'=>  3,
		 'cc'=>  3,
		 'dd'=>  3,
		 'ee'=>  3,
		 'ff'=>  3,
		 'gg'=>  3,
		 'hh'=>  3,
		 'ii'=>  3,
		 'jj'=>  3,
		 'kk'=>  3,
		 'll'=>  3,
		 'mm'=>  3,
		 'nn'=>  3,
		 'oo'=>  3,
		 'pp'=>  3,
		 'qq'=>  3,
		 'rr'=>  3,
		 'ss'=>  3,
		 'tt'=>  3,
		 'uu'=>  3,
		 'vv'=>  3,
		 'ww'=>  3,
		 'xx'=>  3,
		 'zz'=>  3,
	 );
	return $arr[$data];
}

function do_run ($fnc) {
	$start = microtime(true);
	echo "start $fnc ... ";
  // 100万回ループ
	for ($i = 0; $i < 1000000; $i++) {
		$fnc("qq");
	}
	echo "Finish: " . (microtime(true) - $start) . "\n";
}

do_run("arr");
do_run("sw");