PHP登录应用JSON响应触发SyntaxError错误求助

I was stuck with a frustrating SyntaxError: JSON.parse: unexpected character error in Firefox when my PHP login app returned JSON via AJAX. I tried all the usual fixes but none worked:

• Tweaking and even disabling the mbstring extension
• Saving files as "UTF-8 without BOM" in Notepad++
• Adding ob_clean() to clear output buffers

Relevant Code Snippets #

PHP Login Logic:

if($veri[0] == 'TRUE' && $veri[1] == 'TRUE'){
    if(isset($_POST['js']) && $_POST['js'] == 'ajax'){
        header('Content-type: application/json');
        echo json_encode(array('login'=>true,'redi'=>true,'url'=>'./?p=publicar'));
        exit();
    }
}

JavaScript AJAX Handler:

function ajax(){
    this.respuesta;
    this.ajaxCall = function(f, method, url, callback){
        try{
            var x = new XMLHttpRequest();
            x.open(method, url);
            x.onreadystatechange = function(){
                if(x.status == 200 && x.readyState == 4){
                    this.respuesta = x.responseText;
                    if(x.getResponseHeader('Content-type') == 'text/html'){
                        callback(this.respuesta);
                    }else if(x.getResponseHeader('Content-type') == 'application/json'){
                        this.respuesta = JSON.parse(x.responseText);
                        if(this.respuesta.login == true){
                            window.location = this.respuesta.url;
                            document.removeEventListener('keydown', function(){
                                if(evt.keyCode == 27){ }
                            });
                        }
                    }
                }else{
                    this.respuesta = false;
                }
            }
            if(method=='GET'){
                x.send(f);
            }else if(method=='POST'){
                x.send(f);
            }
        }catch(e){ pass('Error'); }
    }
}

The Fix That Worked #

After hours of troubleshooting, the solution ended up being straightforward:

1. Copy the code from each PHP page into a new, blank PHP file created in Dreamweaver or Notepad++
2. Use the editor's "Convert to UTF-8 WITHOUT BOM" feature on the new file
3. Save all these fresh files into a completely new folder (to avoid any residual hidden characters or corrupted metadata from the original directory)

This wiped out the invisible unexpected characters that were breaking the JSON parsing.

内容的提问来源于stack exchange，提问作者Shampoo