如果我们使用sqlite数据库，那么int类型的字段，读取出来的值会是string类型的，
比如：
id name age 1 Jame 20
php读取出来后，变成：
$arr = array( 'id' => '1', 'name' => 'Jame', 'age' => '20' ); 这时候可能就需要转换成int类型了，有三种方式(int)$val、intval($val)、$val + 0
示例代码：
<?php $arr = ['1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1','1','1','1','1','1','1','1', '1','1','1','1','1','1','1','1']; $arr1 = $arr; $arr2 = $arr; $rs = []; list($usec, $sec) = explode(" ", microtime()); $s_time = $usec + $sec; foreach($arr as $val) { foreach($arr1 as $val1) { foreach($arr2 as $val2) { $rs[] = (int)$val2; } } } list($usec, $sec) = explode(" ", microtime()); $e_time = $usec + $sec; echo $e_time - $s_time; //输出：0.50002908706665 $rs = []; list($usec, $sec) = explode(" ", microtime()); $s_time = $usec + $sec; foreach($arr as $val) { foreach($arr1 as $val1) { foreach($arr2 as $val2) { $rs[] = $val2 + 0; } } } list($usec, $sec) = explode(" ", microtime()); $e_time = $usec + $sec; echo '<br/>';echo $e_time - $s_time; //输出：0.46302604675293 $rs = []; list($usec, $sec) = explode(" ", microtime()); $s_time = $usec + $sec; foreach($arr as $val) { foreach($arr1 as $val1) { foreach($arr2 as $val2) { $rs[] = intval($val2); } } } list($usec, $sec) = explode(" ", microtime()); $e_time = $usec + $sec; echo '<br/>';echo $e_time - $s_time; //输出：16.925967931747 本机windows7测试：
0.50002908706665 0.46302604675293 16.925967931747
试了很多次，结果都差不多
结论：
$val + 0 最快
(int)$val 次之
intval($val) 最慢，而且相差比较恐怖
所以建议使用(int)$val和$val + 0
