Update: Found a solution! Using chrome developer tools, I've found that the problem is hardcoding src files in /Applications/blahblah. It's looking for the files in localhost/Applications/blahblah. For now, I've copied the .js files it needed in a subdirectory to /Library/WebServer/Documents/ (where localhost seems to start from on my machine) and coded a path to there. Thanks for the help!
Newbie to PHP here. Can't find my answer with some thorough googling and lots of trying to debug myself.
I'm doing everything locally on my own machine.
I have a PHP class which builds an string that makes up an html page in its entirety, then returns it. My index.php script creates an instance of this class and calls the function that returns the html, and echos it the return. When I execute this class, the page comes up blank (using chrome as a browser). When I "view source" on the blank page, I see exactly the html script I had intended to view.
If I copy and paste that html script into a new file, blahblah.html and load blahblah.html directly with chrome, it works just fine.
Possible subtlety: the html string includes a javascript function which pulls from a hard-coded src directory on my machine.
Thanks for the help! Let me know what more information I might provide that could help.
EDIT: Here's the code:
index.php:
<?php
function __autoload($class_name) 
{
  $source = '/Path/To/src/' . $class_name . '.php';
  if (file_exists($source)) require $source; 
  else throw new Exception('class "' . $class_name . '" source file not found. Failed to autoload...');
}
$myweb=new GenHCSplineIrregTime();
echo $myweb->genWeb();
?>
GenHCSplineIrregTime.php:
<?php
class GenHCSplineIrregTime
{
    public function __construct()
    {
        ;
    }
    public function __destruct()
    {
        ;
    }
    public function genWeb()
    {
        return $this->genEntireHTMLFile();
    }
    private function genEntireHTMLFile()
    {        
        $cont="";
        // $cont = $cont . "<!DOCTYPE HTML>\n";
        $cont = $cont . "<HTML>\n<head>\n";
        $cont = $cont . "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\">\n";
        $cont = $cont . "<title>This is my title</title>\n";
        $cont = $cont . "<script type=\"text/javascript\" src=\"http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js\"></script>\n";
        $cont = $cont . "<style type=\"text/css\">\n\${demo.css}\n</style>\n";
        $cont = $cont . "<script type=\"text/javascript\">\n";
        $cont = $cont . "\$(function () {\n\n$('#container').highcharts({\nchart: {\ntype: 'spline'\n},\n title: {\ntext: 'BATTERY SHIT'\n},\nsubtitle: {\ntext: 'Irregular time data in Highcharts JS'\n},\n";
        $cont= $cont . "xAxis: {\ntype: 'datetime',\ndateTimeLabelFormats: {\nmonth: '%e. %b',\nyear: '%b'\n},\ntitle: {\ntext: 'Date'\n}\n},\n";
        $cont= $cont . "yAxis: {\ntitle: {\ntext: 'Snow depth (m)'\n},\nmin: 0\n},\ntooltip: {\nheaderFormat: '<b>{series.name}</b><br>',\npointFormat: '{point.x:%e. %b}: {point.y:.2f} m'\n},\n";
        //data starts here
        $cont= $cont . "series: [{\nname: 'Winter 2007-2008',\ndata: [\n";
        $cont= $cont . "[Date.UTC(1970,  9, 27), 0   ],\n";
        $cont= $cont . "[Date.UTC(1970, 10, 10), 0.6 ],\n";
        $cont= $cont . "[Date.UTC(1970, 10, 18), 0.7 ]\n]\n}]\n";
        $cont= $cont . "});\n});\n";
        $cont= $cont . "</script>\n</head>\n<body>\n";
        $cont= $cont . "<script src=\"/Applications/BasicSoftware/Highcharts-4.0.3/js/highcharts.js\"></script>\n";
        $cont= $cont . "<script src=\"/Applications/BasicSoftware/Highcharts-4.0.3/js/modules/exporting.js\"></script>\n";
        $cont= $cont . "<div id=\"container\" style=\"min-width: 310px; height: 400px; margin: 0 auto\"></div>\n";
        $cont= $cont . "</body>\n</html>\n";
        return $cont;
    }
    private function fetchData()
    {
        $data="";
        return $data;
    }
}
?>


HTMLcode is outputted to a page, any web browser will process it. EDIT: Unless there's a mime-type issue with the server or lack of server...