Performance of str_replace in PHP

Question

Here I have 2 methods using str_replace to replace strings in a given phrase.

// Method 1
$phrase  = "You should eat fruits, vegetables, and fiber every day.";
$healthy = array("fruits", "vegetables", "fiber");
$yummy   = array("pizza", "beer", "ice cream");
$phrase = str_replace($healthy, $yummy, $phrase);

// Method 2
$phrase  = "You should eat fruits, vegetables, and fiber every day.";
$phrase = str_replace("fruits", "pizza", $phrase);
$phrase = str_replace("vegetables", "beer", $phrase);
$phrase = str_replace("fiber", "ice cream", $phrase);

Which method is more efficient (in terms of execution time & resources used)?

Assume the real phrase is much longer (e.g. 50,000 characters), and the words to replace have a lot more pairs.

What I am thinking is that Method 2 calls str_replace 3 times, which will cost more function calls; on the other hand Method 1 create 2 arrays, and the str_replace needs to parse 2 arrays in runtime.

Answer 1

I would prefer to use method 1 as its cleaner and more organised also Method 1 gives opportunity to use pairs from other source eg: bad words table in database. Method 2 would require another loop of sort..

<?php
$time_start = microtime(true);
for($i=0;$i<=1000000;$i++){
    // Method 1
    $phrase  = "You should eat fruits, vegetables, and fiber every day.";
    $healthy = array("fruits", "vegetables", "fiber");
    $yummy   = array("pizza", "beer", "ice cream");
    $phrase = str_replace($healthy, $yummy, $phrase);
}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "Did Test 1 in ($time seconds)\n<br />";



$time_start = microtime(true);
for($i=0;$i<=1000000;$i++){
    // Method2
    $phrase  = "You should eat fruits, vegetables, and fiber every day.";
    $phrase = str_replace("fruits", "pizza", $phrase);
    $phrase = str_replace("vegetables", "beer", $phrase);
    $phrase = str_replace("fiber", "ice cream", $phrase);

}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "Did Test 2 in ($time seconds)\n";
?>  

Did Test 1 in (3.6321988105774 seconds)

Did Test 2 in (2.8234610557556 seconds)

---

Edit: On further test string repeated to 50k, less iterations and advice from ajreal, the difference is so miniscule.

<?php
$phrase  = str_repeat("You should eat fruits, vegetables, and fiber every day.",50000);
$healthy = array("fruits", "vegetables", "fiber");
$yummy   = array("pizza", "beer", "ice cream");

$time_start = microtime(true);
for($i=0;$i<=10;$i++){
    // Method 1
    $phrase = str_replace($healthy, $yummy, $phrase);
}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "Did Test 1 in ($time seconds)\n<br />";



$time_start = microtime(true);
for($i=0;$i<=10;$i++){
    // Method2
    $phrase = str_replace("fruits", "pizza", $phrase);
    $phrase = str_replace("vegetables", "beer", $phrase);
    $phrase = str_replace("fiber", "ice cream", $phrase);

}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "Did Test 2 in ($time seconds)\n";
?>  

Did Test 1 in (1.1450328826904 seconds)

Did Test 2 in (1.3119208812714 seconds)

Answer 2

Even if old, this benchmark is incorrect.

Thanks to anonymous user:

"This test is wrong, because when test 3 starts $phrase is using the results of test 2, in which there is nothing to replace.

When i add $phrase = "You should eat fruits, vegetables, and fiber every day."; before test 3, the results are: Did Test 1 in (4.3436799049377 seconds) Did Test 2 in (5.7581660747528 seconds) Did Test 3 in (7.5069718360901 seconds)"

        <?php
        $time_start = microtime(true);

        $healthy = array("fruits", "vegetables", "fiber");
        $yummy   = array("pizza", "beer", "ice cream");

        for($i=0;$i<=1000000;$i++){
            // Method 1
            $phrase  = "You should eat fruits, vegetables, and fiber every day.";
            $phrase = str_replace($healthy, $yummy, $phrase);
        }
        $time_end = microtime(true);
        $time = $time_end - $time_start;
        echo "Did Test 1 in ($time seconds)<br /><br />";



        $time_start = microtime(true);
        for($i=0;$i<=1000000;$i++){
            // Method2
            $phrase  = "You should eat fruits, vegetables, and fiber every day.";
            $phrase = str_replace("fruits", "pizza", $phrase);
            $phrase = str_replace("vegetables", "beer", $phrase);
            $phrase = str_replace("fiber", "ice cream", $phrase);

        }
        $time_end = microtime(true);
        $time = $time_end - $time_start;
        echo "Did Test 2 in ($time seconds)<br /><br />";




        $time_start = microtime(true);
        for($i=0;$i<=1000000;$i++){
                foreach ($healthy as $k => $v) {
                  if (strpos($phrase, $healthy[$k]) === FALSE)  
                  unset($healthy[$k], $yummy[$k]);
                }                                          
                if ($healthy) $new_str = str_replace($healthy, $yummy, $phrase);

        }
        $time_end = microtime(true);
        $time = $time_end - $time_start;
        echo "Did Test 3 in ($time seconds)<br /><br />";

        ?>  

Did Test 1 in (3.5785729885101 seconds)

Did Test 2 in (3.8501658439636 seconds)

Did Test 3 in (0.13844394683838 seconds)