why get 404 error when the PHP echo position is changed - php

Question

<?php
define('PATH', dirname(dirname(__FILE__)).'/');
require_once (PATH.'./wp-blog-header.php');
global $wpdb;
// if(!isset($_POST['username'])){
// //echo $_POST['submit'];
// exit('非法访问!');
// }
$username = $_POST["username"];
$password = $_POST["password"];
$email = $_POST["email"];
$checkcode = $_POST["checkcode"];
$query_pwd_str = "SELECT password FROM yjhy_users_custom WHERE username=%s";
if($wpdb == null)
echo "wpdb is null";
$pwd_query_result = $wpdb->get_results($wpdb->prepare($query_pwd_str, $username));
$pwd_query_result_count = count($pwd_query_result);
if($pwd_query_result_count == 1){
//已经存在该用户名，返回数据
// error here
header('Content-type:text/json');
$json_ouput = '{"status":"success","errormsg":"'.$username.'"}';
echo $json_ouput;
}
?>
With the code above, I use method post to refer to the php file, and it ALWAYS responsed with 404 Error.
But, when I modify PHP code as BELOW:
<?php
//****************** move the function header() here
header('Content-type:text/json');
//****************** echo "{" here
echo "{";
?>
<?php
define('PATH', dirname(dirname(__FILE__)).'/');
require_once (PATH.'./wp-blog-header.php');
global $wpdb;
// if(!isset($_POST['username'])){
// //echo $_POST['submit'];
// exit('非法访问!');
// }
$username = $_POST["username"];
$password = $_POST["password"];
$email = $_POST["email"];
$checkcode = $_POST["checkcode"];
$query_pwd_str = "SELECT password FROM yjhy_users_custom WHERE username=%s";
if($wpdb == null)
echo "wpdb is null";
$pwd_query_result = $wpdb->get_results($wpdb->prepare($query_pwd_str, $username));
$pwd_query_result_count = count($pwd_query_result);
if($pwd_query_result_count == 1){
//已经存在该用户名，返回数据
// error here
$json_ouput = '"status":"success","errormsg":"'.$username.'"';
echo $json_ouput;
}
?>
<?php
//****************** echo "}" here
echo "}";
?>
AND THEN, it works, the server response status is 200!
I'm puzzled about this problem, and have searched all day and can't find the answer!
Why does the code work like this?

Answer 1

With 1 days' time, I find it out!
I request the link with the file path http://localhost:7770/api/register.php directly rather than request link by creating a page in the Dashboard, so the link is not in the WP's database.
And WP framework need to initialize itself when execute wp(); in the require_once (PATH.'./wp-blog-header.php');, but when the initial action execute in the file /wp-includes/class-wp.php with code below:
public function main($query_args = '') {
$this->init();
**$this->parse_request($query_args);**
$this->send_headers();
$this->query_posts();
$this->handle_404();
$this->register_globals();
do_action_ref_array( 'wp', array( &$this ) );
}
}
the statement $this->query_posts(); need to check the link $this->parse_request();. the func parse_request():
public function parse_request($extra_query_vars = '') {
global $wp_rewrite;
/**
* Filter whether to parse the request.
*
* #since 3.5.0
*
* #param bool $bool Whether or not to parse the request. Default true.
* #param WP $this Current WordPress environment instance.
* #param array|string $extra_query_vars Extra passed query variables.
*/
if ( ! apply_filters( 'do_parse_request', true, $this, $extra_query_vars ) )
return;
$this->query_vars = array();
$post_type_query_vars = array();
if ( is_array( $extra_query_vars ) ) {
$this->extra_query_vars = & $extra_query_vars;
} elseif ( ! empty( $extra_query_vars ) ) {
parse_str( $extra_query_vars, $this->extra_query_vars );
}
// Process PATH_INFO, REQUEST_URI, and 404 for permalinks.
// Fetch the rewrite rules.
$rewrite = $wp_rewrite->wp_rewrite_rules();
if ( ! empty($rewrite) ) {
// If we match a rewrite rule, this will be cleared.
***$error = '404';***
$this->did_permalink = true;
$pathinfo = isset( $_SERVER['PATH_INFO'] ) ? $_SERVER['PATH_INFO'] : '';
list( $pathinfo ) = explode( '?', $pathinfo );
$pathinfo = str_replace( "%", "%25", $pathinfo );
list( $req_uri ) = explode( '?', $_SERVER['REQUEST_URI'] );
$self = $_SERVER['PHP_SELF'];
$home_path = trim( parse_url( home_url(), PHP_URL_PATH ), '/' );
And the link is not in the database, so WP set the error 404 here below:
And then I get the error 404in ***$error = '404';***!
resolve solution:
create a page in the Dashboard.
modify the page url you want.
put your code in the page template.
use this template in the page.
and Ok