如何输出php？

I am struggling on an AJAX call I make to let me read out the return value. My php code returns automatically an echo with false or true, which I made to check if the mail was send. But I am struggling to read out the value and get it to work.

Here is my AJAX code

if(proceed == true){            
    $.ajax({
        type    : 'POST',
        url     : 'inc/actions/sendmail.php',
        data    : $('#sentMessage').serialize(),
        cache   : false,
        dataType: 'text',
        success : function (data) 
        { 
            if (data == 'true'){
                $("#sentMessage")[0].reset();
                $("#err").append("<div class='alert alert-success' role='alert'>Bedankt voor je bericht, wij nemen binnenkort contact met je op.</div>");
                $('input[name=name]').css('border-color','')
                $('input[name=email]').css('border-color','')
                $('textarea[name=message]').css('border-color','')
                setTimeout(function(){$('#err').fadeOut();}, 5000);
            }else{
                $("#err").append("<div class='alert alert-danger' role='alert'>Je telefoonnummer bestaat niet uit 10 cijfers.</div>");
                $('input[name=phone]').css({'border':'2px solid red'});
                setTimeout(function(){$('#err').fadeOut();}, 5000); 
            }
        },
        error   : function (jqXHR, textStatus, errorThrown) {console.log(errorThrown);}
    }); 
}

As you figure, it will push out the else statement constantly, cause it doesn't pass the if statement, since it doesn't know what to check.

You should try console.log(data) to check exactly what your server is returning. There is also a change it is an object that is being returned, so you may need console.log(JSON.stringify(data)).

Also, this probably is not related but you should always be using triple equals (===), it is good practice in JavaScript.

Even though all you're outputting is true/false from your PHP script, and even after you've confirmed that console.log( data ) outputs true/false, there may be white spaces around the string. Therefore you may want to use:

if( data.trim() == 'true' ) { ....

if( data.indexOf('true') > -1 ) { ..... //<=== OR

Just to confirm, you may want to use:

console.log( "'" + data + "'" );