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POisset() vs strlen() - a fast/clear string length calculation
 

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    <p>I came across this code...</p> <pre><code>if(isset($string[255])) { // too long } </code></pre> <p>isset() is between 6 and 40 faster than </p> <pre><code>if(strlen($string) &gt; 255) { // too long } </code></pre> <p>The only drawback to the isset() is that the code is unclear - we cannot tell right away what is being done (see pekka's answer). We can wrap isset() within a function i.e. strlt($string,255) but we then loose the speed benefits of isset().</p> <p><strong>How can we use the faster isset() function while retaining readability of the code?</strong> </p> <p>EDIT : test to show the speed <a href="http://codepad.org/ztYF0bE3" rel="nofollow noreferrer">http://codepad.org/ztYF0bE3</a></p> <pre><code>strlen() over 1000000 iterations 7.5193998813629 isset() over 1000000 iterations 0.29940009117126 </code></pre> <p>EDIT2 : here's why isset() is faster</p> <pre><code>$string = 'abcdefg'; var_dump($string[2]); Output: string(1) “c” $string = 'abcdefg'; if (isset($string[7])){ echo $string[7].' found!'; }else{ echo 'No character found at position 7!'; } </code></pre> <p>This is faster than using strlen() because, “… calling a function is more expensive than using a language construct.” <a href="http://www.phpreferencebook.com/tips/use-isset-instead-of-strlen/" rel="nofollow noreferrer">http://www.phpreferencebook.com/tips/use-isset-instead-of-strlen/</a></p> <p>EDIT3 : I was always taught to be interested in mirco-optimisation. Probably because I was taught at a time when resources on computers were tiny. I'm open to the idea that it may not be important, there are some good arguments against it in the answers. I've started a new question exploring this... <a href="https://stackoverflow.com/questions/6983208/is-micro-optimisation-important-when-coding">https://stackoverflow.com/questions/6983208/is-micro-optimisation-important-when-coding</a></p>
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    1. COI think the second one is still faster, since PHP internally keeps track of a string's length.
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    2. COHm, how are strings implemented in PHP - null-terminated or length-prefixed? That'd make a big difference.
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    3. COhttp://codepad.org/IGKfD2Mk I copy/pasted your code and don't have the same result at all :D
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