<?php
$arr = array();
for ($i = 0; $i < 1000; $i++) $arr[] = rand(-100, 100);
$start = microtime(true);
for ($i = 0; $i < 1000; $i++){
foreach ($arr as $v) $v = abs($v);
}
echo number_format(microtime(true) - $start, 4).'<br />';
$start = microtime(true);
for ($i = 0; $i < 1000; $i++){
foreach ($arr as $v) if ($v < 0) $v = abs($v);
}
echo number_format(microtime(true) - $start, 4).'<br />';
$start = microtime(true);
for ($i = 0; $i < 1000; $i++){
foreach ($arr as $v) if ($v < 0) $v *= -1;
}
echo number_format(microtime(true) - $start, 4).'<br />';
?>
Result:
1.4061
0.9697
0.2805
Conclusion: better to check before using the feature that the number is less than zero. Even better use multiplication by -1 than this function.