Syntax for single-line comments

                    
<?php
    // This is a single-line comment
    # This is also a single-line comment
?>
                    
                

Syntax for multi-line comments

                    
<?php
    /*
    This is a multiple-lines comment block
    that spans over multiple
    lines
    */
?>
                    
                

Using comments to leave out parts of the code

                    
<?php
    // You can also use comments to leave out parts of a code line
    $x = 5 /* + 15 */ + 5;
    echo $x;
?>