PHP randomly stops output when displaying MySQL Result

[DeX3]

Hey there,

I'm relatively new to PHP and I got a problem I just cannot seem to solve. I have to display a <select>-box filled with values from a MySQL-database. Since I have to do this very often and for a lot of different tables, I wrote this function:

/****************************************************************************
 * Prints a <select>-Combobox
 * $sql(String): An SQL-Statement, used to gather the data vor the box
 * $name(String): The name vor the <select>
 * $keyCol(int): The column in the result from $sql, which contains the value for the value-property of the different <option>-tags
 * $valueCol(int): THe column in the result from $sql, which contains the text for the different <option>-tags 
 * $selected(String): A value, that should be preselected
 * $includeNoVal(Boolean): if true, the printed <select> will contain a "Not specified"-option
 * *************************************************************************/   
function printComboBox( $sql, $name, $keyCol, $valueCol, $selected, $includeNoVal=true )
{
    $db = db_connect();
    
    $tmp = mysql_query( $sql, $db );
    
    var_dump( $tmp );     //for testing purposes
    
    if( $tmp )
    {
        echo "<select size=\"1\" name=\"" . htmlspecialchars($name) . "\">\n"; //Start the <select>
        
        if( $includeNoVal )             //There shall be a "Not specified"-option
        {
            echo "\t<option value=\"NULL\"";
            
            if( !isset( $selected ) )        //If there is no preselection specified
                echo " selected";           //Preselect the "Not specified" option
                
             echo ">Not specified</option>\n";
        }
        
        while( $tmpRow = mysql_fetch_row( $tmp ) )
        {
            var_dump( $tmpRow );         //For testing purposes
        
            echo "\t<option value=\"" . htmlspecialchars($tmpRow[$keyCol]) . "\"";                  //Print the start of the <option>-tag
            
            if( $selected == $tmpRow[$keyCol] )     //Check wether this <option> needs to be preselected
                echo " selected";
                
            echo ">" . htmlspecialchars( $tmpRow[$valueCol] ) . "</option>\n";  //Close the option-tag
        }
        echo "</select>\n";       //End of the <select>
    }else
        throw new DBException( "Unable to retrieve data for \'" . $name . "\'", mysql_errno() );
} 

Here's how I use it (Note: $edit[1] contains the value to preselect):

<?php printComboBox( "SELECT id, name FROM departments", "department", 0, 1, $edit[1] ); ?>

The Problem is, that PHP behaves really strange when I run this code. Sometimes, it works just fine (~50% of the time). However, sometimes PHP just seems to randomly stop the output. Sometimes it even stops WITHIN one of the test-vardumps (Very special in this case: it even puts out some text that looks like the text "domain." displayed with the wrong encoding):

<select size="1" name="department">
[...]
<option value="114">Some test department here
</option>
array(2) {
  [0]=>
  string(3) "115"
  [1]=>
  string(13) "Some test department here
"
}
	<option value="115">Another test department

</option>
array(2) {
  [0]=>
  string(3) "116"
  [1]=>
  string(9) "d�o�m�a�i�n�.�

I have absolutely no idea what is going wrong there. As I said, WHERE it stops seems completely random. Sometimes it's in the middle of an echo, sometimes it's like above, within a call of var_dump. And sometimes it works just fine.

All the searching I did, didn't give me a solution, hope you can help me =)

thx in advance