function strReverse($str)
{
    $rev = "";
    $length = strLength($str);
    for ($i = $length; $i >= 0; $i--) {
        $rev .= $str[$i];
    }
    return $rev;
}
 public function add_introduce()
 {
     if (IS_POST) {
         $data = $this->CommonController->getRequestData();
         $data = $this->CommonController->arr2ToArr($data['data']);
         if (!trim($data['dear_hr'])) {
             $error['msg'] = '必填';
             $error['status'] = FALSE;
             $error['code'] = $this->controller_code + 1;
             returnjson($error);
         }
         if (!strLength($data['dear_hr'], 300)) {
             $error['msg'] = '限300字内';
             $error['status'] = FALSE;
             $error['code'] = $this->controller_code + 2;
             returnjson($error);
         }
         //对是否存在dearHr进行判断
         $student_result = $this->StudentModel->field('dear_hr')->find(session('account.student_id'));
         $bool = $this->StudentModel->update_introduce($data['dear_hr']);
         if ($bool) {
             if (empty($student_result['dear_hr'])) {
                 $stData = array('pkid' => session('account.student_id'), 'complete_rate' => array('exp', 'complete_rate+' . $this->rate_base));
                 $this->StudentModel->save($stData);
             }
             $error['msg'] = '添加成功';
             $error['status'] = TRUE;
             $error['code'] = $this->controller_code + 3;
             $error['data'] = textareaFormat($this->introduceTpl());
             // ;
             returnjson($error);
         } else {
             $error['msg'] = '添加失败';
             $error['status'] = FALSE;
             $error['code'] = $this->controller_code + 4;
             returnjson($error);
         }
     }
 }
<html>
	<?php 
if (isset($_GET['string'])) {
    $string = $_GET['string'];
    $result = strLength($string);
    echo $result;
}
function strLength($string)
{
    $i = 0;
    $count = 0;
    while (isset($string[$i])) {
        $count = $count + 1;
        $i++;
    }
    return $i;
}
?>
	<body>
		<form action="own_str_length.php" method="get" align="center">
		Given String: <input type="text" name="string"><br><br>
		
		<button type="submit">Result</button>
		</form>
	</body>
</html>
<?php 
include "own_str_length.php";
$str = "Hello FTFL";
$length = strLength($str);
for ($i = $length; $i >= 0; $i--) {
    echo $str[$i];
}
 function setLength($string)
 {
     $result = strLength($string);
     $this->str = $result;
     return $this->str;
 }