A "pitfall" and "pitfall" in PHP _ PHP Tutorial-PHP Tutorial

A "pitfall" in PHP and a "pitfall" in PHP ". A "pitfall" in PHP, the PHP pitfall says a foreach reference to a very likely problem at work $ arrrange (); [, 3] foreach ($ arras $ val) {} foreach ($ arras $ A "pitfall" in PHP, "pitfall" in PHP"

A problem that is very likely to be encountered at work -- reference of foreach

$arr = range(1,3);//[1,2,3]foreach($arr as &$val) {}foreach($arr as $val) {}print_r($arr); 

What is the output of the above code? what's amazing is the following: I met this once at work. I didn't come up with a solution after a long time, but I found a solution, there are two solutions to this problem:

Array(    [0] => 1    [1] => 2    [2] => 2)

Both of the following methods can solve the above problem:

// Method 1 foreach ($ arr as & $ value) {} unset ($ value); foreach ($ arr as $ value) {} print_r ($ arr ); // [, 3] // method 2 foreach ($ arr as & $ value) {} foreach ($ arr as $ val) {} print_r ($ arr ); // [, 3] // method 3 foreach ($ arr as & $ value) {} print_r ($ arr ); // [1, 2, 3]

Method 1 you can also see http://php.net/manual/en/control-structures.foreach.php in the official manual. in this document, a dedicated tipsprompts that the response callback var = 123; $ tmp = & $ var; $ tmp = 200; echo $ var; // 200

Take a look at the stolen figure below (haha, the original article link is posted below) to better understand the above

1, "B" => 2, "c" => 3); $ arr2 = array ("x" => 4, "y" => 5, "z" => 6); foreach ($ arr1 as $ key => & $ val) {} foreach ($ arr2 as $ key => $ val) {} var_dump ($ arr1); var_dump ($ arr2);?> The output is: array (3) {["a"] => int (1) ["B"] => int (2) ["c"] => & int (6)} array (3) {["x"] => int (4) ["y"] => int (5) ["z"] => int (6 )}

References:

Http://www.cnblogs.com/CraryPrimitiveMan/p/4030748.html#3085766

Http://www.jb51.net/article/39299.htm

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When "pitfall" says a problem that is very likely to be encountered at work foreach references $ arr = range (1, 3); // [1, 2, 3] foreach ($ arr as $ val) {} foreach ($ arr as $...