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POPHP script unexpectedly not continuing
 

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    <p>I have a PHP script (let's call it <code>execute.php</code>) that draws the whole page (HTML tags and body tags etc.) at the beginning and, afer that, executes some commands (C++ programs) in the background. It then waits for these programs to terminate (some depend on the results of others, so they may be executed sequentially) and then has a JavaScript that auto-submits a form to another PHP script (which we will call <code>results.php</code>) because <code>results.php</code> needs the POST-information from the previous script.</p> <p><code>execute.php</code>:</p> <pre><code>&lt;?php print" &lt;html&gt; &lt;body&gt; Some HTML code here &lt;/body&gt; &lt;/html&gt; "; // Here come some C++-program calls $pid_program1 = run_in_background($program1) $pid_program2 = run_in_background($program2) while (is_running($pid_program1) or is_running($pid_program2) ) { //echo("."); sleep(1); } // Here come some later C++-program calls that execute quickly $pid_program3 = run_in_background($program3) $pid_program4 = run_in_background($program4) while (is_running($pid_program3) or is_running($pid_program4) ) { sleep(1); } ... // We are now finished print " &lt;form action=\"results.php\" id=\"go_to_results\" method=\"POST\"&gt; &lt;input type='hidden' name=\"session_id\" value=\"XYZ\"&gt; &lt;/form&gt; &lt;script type=\"text/javascript\"&gt; AutoSubmitForm( 'go_to_results' ); &lt;/script&gt; "; </code></pre> <p>This works nicely if the C++ programs 1 and 2 execute quickly. However, when they take their time (around 25 minutes in total), the PHP script seems to fail to continue. Interestingly the C++ programs 3 and 4 are nevertheless executed and produce the expected outputs etc.</p> <p>However, when I put a <code>echo(".");</code> in the first while-loop before the <code>sleep()</code>, it works and continues until the JavaScript autosubmit.</p> <p>So it seems to me that the remaining PHP code (including the autosubmit) is, for whatever reason, not send when there is no output in the first <code>while</code> loop.</p> <p>I have also tried using <code>set_time_limit(0)</code> and <code>ignore_user_abort(true)</code> and different other things like writing to an outputbuffer (don't want to clutter the already finally displayed webpage) instead of the echo, but none of these work.</p> <p>When I run the same scripts on a machine with multiple cores, so that program1 and 2 can be executed in parallel, it also works, without the <code>echo(".")</code>.</p> <p>So I am currently very confused and can't find any error messages in the apache log or PHP log and thus would really appreciate your thoughts on this one.</p> <p><strong>EDIT</strong> Thanks again for your suggestions so far. I have now adopted a solution involving (really simple) AJAX and it's definitely nicer this way. However, if the C++-programs executions take "longer" it is not autosubmitting to the results-page, which is actually created this time (failed to do so before). Basically what I have done is:</p> <pre><code> process.php: &lt;?php $params = "someparam=1"; ?&gt; &lt;html&gt; &lt;body&gt; &lt;script type="text/javascript"&gt; function run_analyses(params){ // Use AJAX to execute the programs independenantly in the background // Allows for the user to close the process-page and come back at a later point to the results-link, w/o need to wait. if (window.XMLHttpRequest) { http_request = new XMLHttpRequest(); } else { //Fallback for IE5 and IE6, as these don't support the above writing/code http_request = new ActiveXObject("Microsoft.XMLHTTP"); } //Is http_request still false if (!http_request) { alert('Ende :( Kann keine XMLHTTP-Instanz erzeugen'); } http_request.onreadystatechange=function(){ if (http_request.readyState==4 &amp;&amp; http_request.status==200){ // Maybe used to display the progress of the execution //document.getElementById("output").innerHTML=http_request.responseText; // Call of programs is finished -&gt; Go to the results-page document.getElementById( "go_to_results" ).submit(); } }; http_request.open("POST","execute.php",true); //Send the proper header information along with the request http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); http_request.setRequestHeader("Content-length", params.length); http_request.setRequestHeader("Connection", "close"); http_request.send(params); }; &lt;/script&gt; &lt;?php // Do some HTML-markup ... // Start the programs! print " &lt;script type=\"text/javascript\"&gt; run_analyses('".$params."'); &lt;/script&gt; &lt;form action=\"results.html" id=\"go_to_results\" method=\"POST\"&gt; &lt;input type='hidden' name=\"session_id\" value=\"XYZ\"&gt; &lt;/form&gt; ?&gt; &lt;/html&gt; &lt;/body&gt; </code></pre> <p>and execute.php contains the C++-program calls, waiting-routines and finally, via "include("results.php")" the creation of the results-page. Again, for "not so long" program executions, the autosubmission works as expected, but not if it takes "longer". By "longer" I mean around 25 minutes.</p> <p>I have absolutely no idea what could cause this as again, there are no error-messages to be found. Am I missing a crucial configuration option there (apache, php, etc.)?</p> <p><strong>EDIT</strong> As it turned out, letting the requested PHP-script "echo" something repeatedly prevents the timeout. So it is basically the same as for the PHP-solution without AJAX, but this time, since the responseText of the AJAX-request is not necessarily needed, the progress-page is not cluttered and it may be used as a workaround. Specifically, I would not necessarily recommend it a as a general solution or good-practice.</p>
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    1. COHow are you invoking `execute.php`? By an `http` request, or command line?
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