PHP Array Traversal performance comparison _php tutorial

The For loop is limited to numeric indexes, and the for and foreach loops do not require the reset () operation to be performed for the next traversal, and each method requires

!--? php tutorial
//a
$arr =array (' a ' = ' abc ', ' B ' =>123, ' C ' =>true);
b
//$arr =range (' A ', ' d ');

//1
for ($i =0; $i echo $arr [$i]. ', ';
Echo '
';

//2
foreach ($arr as $key)
echo "$key,";
Echo '
';

//3
foreach ($arr as $key = + $val)
echo "$key-$val,";
Echo '
';

//4
Reset ($arr);
while ($item =each ($arr)) {
echo $item [' key ']. -'. $item [' value ']. ', ';
}
Echo '
';

//5
Reset ($arr);
while (list ($key, $val) =each ($arr)) {
echo ' $key-$val, ";
}
Echo '
';
? > Use Statement a $arr =array (' a ' = ' = ' abc ', ' B ' =>123, ' C ' =>true); Initialize the $arr to get a numeric index array, output as follows:

,,,
ABC, 123, 1,
A-abc, b-123, C-1,
A-abc, b-123, C-1,
A-abc, b-123, c-1, make Use statement b $arr =range (' A ', ' d '); Initialize the $arr to get an associative array with the output as follows:

A, B, C, D,
A, B, C, D,
0-a, 1-b, 2-c,-D,
0-a, 1-b, 2-c, D-,
0-a, 1-b, 2-c, -I,

After repeated tests, the result shows that for traversing the same array, the foreach speed is the fastest and the slowest is the while. The foreach is about 20% ~ 30% faster than while. The array subscript is then incremented to 500000, and the 5000000 test results are the same. In principle, however, foreach operates on an array copy (by copying the arrays), while the while is manipulated by moving the internal indicators of the array, which is generally considered to be faster than foreach (since foreach first copies the array in the beginning of execution). While the while moves the internal indicator directly. ), but the result is just the opposite. The reason for this is that foreach is an internal implementation of PHP, while the while is a common loop structure

http://www.bkjia.com/PHPjc/444745.html www.bkjia.com true http://www.bkjia.com/PHPjc/444745.html techarticle The for loop is only limited to numeric indexes, and the for and foreach traversal does not require the reset () operation to be performed for the next iteration, and each method needs to be? PHP tutorial//a $arr =array (' a ' = ' a ...

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