Adding short comments to your code is recommended and usually a requirement in larger software houses. In PHP you have three options for commenting style: //, /* */, and #. The first option (two slashes) instructs PHP to ignore everything until the end of the line. The second (a slash and an asterisk) instructs PHP to ignore everything until it reaches */. The last (a hash symbol) works like // and is included because it is common among shell scripting languages.
This code example demonstrates the difference between // and /* */:
// echo "This is not printed";
echo "This is printed!";
/* echo "This is not printed";
echo "This is not printed either"; */
It is generally preferred to use // because it is a known quantity. On the other hand, it is easy to introduce coding errors with /* */ by losing track of where a comment starts and ends.
Contrary to popular belief, having comments in your PHP script has almost no effect on the speed at which the script executes. What little speed difference exists is wholly removed if you use a code cache.
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