<?php
$limit = 1000 * 1000;
$inject = 'injection string';
$start = microtime(true);
for ($i = 0; $i < $limit; $i++) {
 
}
$empty = microtime(true) - $start;
$start = microtime(true);
for ($i = 0; $i < $limit; $i++) {
	$str = "beginning [$inject] end";
}
$double = microtime(true) - $start;
$start = microtime(true);
for ($i = 0; $i < $limit; $i++) {
	$str = 'beginning ['.$inject.'] end';
}
$single = microtime(true) - $start;
var_dump($empty, $double, $single, $double - $empty, $single - $empty);
 

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