除非使用调整大小或单击功能，否则不会加载函数

I want to execute a function which was defined in the start of the script, lets call this function initialize. This function also uses a variable, lets call it login, which is defined by a php file that includes my jquery script file after defining the variable login.

php/html:

<script type="text/javascript">

login           = '<?php echo $login; ?>';
...
</script>
<!-- script is included -->
<script type="text/javascript" src="script.js"></script>

jquery:

function initialize(){
    $("." + login).remove();
}

jQuery.moreContent = function moreContent()
{
    //more content is loaded
    ...
    initialize();
}

the moreContent function is then loaded, I can see more content appearing on my screen but initialiye is not loaded. only if I use a function like resize (in the end of the script.js file) it works

jquery (in the end of script):

//load function initialize
initialize();
//this function doesnt work too, I tested if it even loads and it does (used a number that was increased by one whenever function was loaded which actually happened...)
//however the wished element with the class of variable login is not removed

//resize function
$(window).resize(initialize);
//this one suddenly works 
...

I have no idea why it suddenly works with the other function and why it doesnt work in the other cases

You need to wrap your code and make it run once the document is ready, like this:

$(document).ready (function(){
    // run all your functions here
});

Maybe the variable login is empty in the other function, or you are giving thst a different value.

Try with a global variable to test it, like

window.login = script_php

And try again, in this ways, the login variable is global, or pass this variable as a parameter in the function.

the moreContent function is then loaded, I can see more content appearing on my screen but initialize is not loaded.

That is not exactly what happened. You have attached a function as method directly to jQuery object but did not invoke it,

jQuery.moreContent = function moreContent()
{
    //more content is loaded
    ...
    initialize();
}

You won't get any fruitful benefit from doing it this way. You have just added a method to an object (jQuery in this case) which is not invoked yet. In any case you do not need to add it as a method to jQuery object itself. You can do it easily without this as following.

function initialize(){
    $("." + login).remove();
}

// this is a global function right now, use it anywhere you want.
function moreContent()
{
    //more content is loaded
    ...
    initialize();
}

// document ready...
$(function(){
    moreContent();
});

You can rearrange the code and remove the unnecessary function layers (depends upon your code structure) and use it like this.

$(function(){
    // more content...

    initialize();
});

if I use a function like resize (in the end of the script.js file) it works

It worked because it is attached directly to window by jQuery on resize event.

$(window).resize(function(){
    // The code inside will work whenever user resizes the window.
    // It does not need to be hooked up inside document ready.
});

I have no idea why it suddenly works with the other function and why it doesnt work in the other cases

The reason it worked inside event handlers is because you hooked up your functions to run as a callback function to them. You have set it up correctly in click or resize event but not in load event. In load event you just created a function and added the it as a method to jQuery object but did not invoke it. The only and only way a function runs inside JavaScript is when you suffix parenthesis.

function demo()
{
    // do something...
    return "Done";
}

// a named function "demo" got created, but not invoked.

demo;  // returns the whole function literal, not invoked yet.

demo(); // invoked, returns Done

So continuing from this, adding it as a method to jQuery will not load it, until you invoke it e.g.

jQuery.myNewMethod = function myNewMethod() {
    return "Hey there :)";
}

// jQuery loaded, but where is my method ?? (@__@)
// let's invoke it then...

jQuery.myNewMethod();  // invoked the function using parenthesis!
// returns "Hey there :)"
// Now i can see you go (^__^)