Detailed explanation about php catching errors

php methods to catch errors: 1. Use the "try{}catch()" method to catch errors; 2. Use the "set_error_handler" function to catch "E_NOTICE", etc.; 3. Use "set_exception_handler" to set the default exception handler.

php error and exception capture

In actual development, error and exception capture only relies on try{}catch () is far from enough.

So quote the following functions.

a) set_error_handler

Generally used to capture E_NOTICE, E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE

Cannot capture:

E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR and E_COMPILE_WARNING.

Generally used in conjunction with trigger_error("...", E_USER_ERROR).

<?php
// we will do our own error handling
error_reporting(0);
function userErrorHandler($errno, $errmsg, $filename, $linenum, $vars)
{
    // timestamp for the error entry    
$dt = date("Y-m-d H:i:s (T)");    
// define an assoc array of error string    
// in reality the only entries we should    
// consider are E_WARNING, E_NOTICE, E_USER_ERROR,    
// E_USER_WARNING and E_USER_NOTICE    
$errortype = array (                
E_ERROR              => &#39;Error&#39;,                
E_WARNING            => &#39;Warning&#39;,                
E_PARSE              => &#39;Parsing Error&#39;,                
E_NOTICE             => &#39;Notice&#39;,                
E_CORE_ERROR         => &#39;Core Error&#39;,                
E_CORE_WARNING       => &#39;Core Warning&#39;,                
E_COMPILE_ERROR      => &#39;Compile Error&#39;,                
E_COMPILE_WARNING    => &#39;Compile Warning&#39;,                
E_USER_ERROR         => &#39;User Error&#39;,                
E_USER_WARNING       => &#39;User Warning&#39;,                
E_USER_NOTICE        => &#39;User Notice&#39;,                
E_STRICT             => &#39;Runtime Notice&#39;,                
E_RECOVERABLE_ERROR  => &#39;Catchable Fatal Error&#39;                
);    
// set of errors for which a var trace will be saved    
$user_errors = array(E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE);        
$err = "<errorentry>\n";    
$err .= "\t<datetime>" . $dt . "</datetime>\n";    
$err .= "\t<errornum>" . $errno . "</errornum>\n";    
$err .= "\t<errortype>" . $errortype[$errno] . "</errortype>\n";    
$err .= "\t<errormsg>" . $errmsg . "</errormsg>\n";    
$err .= "\t<scriptname>" . $filename . "</scriptname>\n";    
$err .= "\t<scriptlinenum>" . $linenum . "</scriptlinenum>\n";    
if (in_array($errno, $user_errors)) {        
$err .= "\t<vartrace>" . wddx_serialize_value($vars, "Variables") . "</vartrace>\n";    
}    
$err .= "</errorentry>\n\n";
echo $err;
}
function distance($vect1, $vect2) {    
if (!is_array($vect1) || !is_array($vect2)) {        
trigger_error("Incorrect parameters, arrays expected", E_USER_ERROR);        
return NULL;    
}    
if (count($vect1) != count($vect2)) {        
trigger_error("Vectors need to be of the same size", E_USER_ERROR);        
return NULL;    
} 
for ($i=0; $i<count($vect1); $i++) {        
$c1 = $vect1[$i]; $c2 = $vect2[$i];        
$d = 0.0;        
if (!is_numeric($c1)) {            
trigger_error("Coordinate $i in vector 1 is not a number, using zero",E_USER_WARNING);            
$c1 = 0.0;        
}        
if (!is_numeric($c2)) {            
trigger_error("Coordinate $i in vector 2 is not a number, using zero",E_USER_WARNING);            
$c2 = 0.0;        
}
$d += $c2*$c2 - $c1*$c1;    
}    
return sqrt($d);
}
 
$old_error_handle = set_error_handler("userErrorHandler");
$t = I_AM_NOT_DEFINED;//generates a warning
 
// define some "vectors"
$a = array(2, 3, "foo");
$b = array(5.5, 4.3, -1.6);
$c = array(1, -3);
 
//generate a user error
$t1 = distance($c,$b);
 
// generate another user error
$t2 = distance($b, "i am not an array") . "\n";
 
// generate a warning
$t3 = distance($a, $b) . "\n";
?>

b) set_exception_handler

Set the default exception handler for exceptions that are not caught with try/catch blocks. Exceptions are aborted after exception_handler is called.

Use together with throw new Exception('Uncaught Exception occurred').

<?php
// we will do our own error handling
error_reporting(0);
function exceptHandle($errno, $errmsg, $filename, $linenum, $vars)
{
    // timestamp for the error entry    
$dt = date("Y-m-d H:i:s (T)");    
// define an assoc array of error string    
// in reality the only entries we should    
// consider are E_WARNING, E_NOTICE, E_USER_ERROR,    
// E_USER_WARNING and E_USER_NOTICE    
$errortype = array (                
E_ERROR              => &#39;Error&#39;,                
E_WARNING            => &#39;Warning&#39;,                
E_PARSE              => &#39;Parsing Error&#39;,                
E_NOTICE             => &#39;Notice&#39;,                
E_CORE_ERROR         => &#39;Core Error&#39;,                
E_CORE_WARNING       => &#39;Core Warning&#39;,                
E_COMPILE_ERROR      => &#39;Compile Error&#39;,                
E_COMPILE_WARNING    => &#39;Compile Warning&#39;,                
E_USER_ERROR         => &#39;User Error&#39;,                
E_USER_WARNING       => &#39;User Warning&#39;,                
E_USER_NOTICE        => &#39;User Notice&#39;,                
E_STRICT             => &#39;Runtime Notice&#39;,                
E_RECOVERABLE_ERROR  => &#39;Catchable Fatal Error&#39;                
);    
// set of errors for which a var trace will be saved    
$err = "<errorentry>\n";    
$err .= "\t<datetime>" . $dt . "</datetime>\n";    
$err .= "\t<errornum>" . $errno . "</errornum>\n";    
$err .= "\t<errortype>" . $errortype[$errno] . "</errortype>\n";    
$err .= "\t<errormsg>" . $errmsg . "</errormsg>\n";    
$err .= "\t<scriptname>" . $filename . "</scriptname>\n";    
$err .= "\t<scriptlinenum>" . $linenum . "</scriptlinenum>\n";    
if (1) {        
$err .= "\t<vartrace>" . wddx_serialize_value($vars, "Variables") . "</vartrace>\n";    
}    
$err .= "</errorentry>\n\n";
echo $err;
}
$old_except_handle = set_exception_handler("exceptHandle");
//$t = I_AM_NOT_DEFINED;//generates a warning
$a;
throw new Exception(&#39;Uncaught Exception occurred&#39;);    
?>

c) register_shutdown_function

The execution mechanism is: php transfers the function to be called into memory. This function is called again when all PHP statements on the page have been executed.

Generally used in conjunction with trigger_error("...", E_USER_ERROR).

<?php
error_reporting(0);
date_default_timezone_set(&#39;Asia/Shanghai&#39;);
register_shutdown_function(&#39;my_exception_handler&#39;);
 
$t = I_AM_NOT_DEFINED;//generates a warning
trigger_error("Vectors need to be of the same size", E_USER_ERROR);     
 
function my_exception_handler()
{
    if($e = error_get_last()) {
    //$e[&#39;type&#39;]对应php_error常量
    $message = &#39;&#39;;
    $message .= "出错信息:\t".$e[&#39;message&#39;]."\n\n";
    $message .= "出错文件:\t".$e[&#39;file&#39;]."\n\n";
    $message .= "出错行数:\t".$e[&#39;line&#39;]."\n\n";
    $message .= "\t\t请工程师检查出现程序".$e[&#39;file&#39;]."出现错误的原因\n";
    $message .= "\t\t希望能您早点解决故障出现的原因<br/>";
echo $message;
    //sendemail to
    }
}
?>

c) restore_error_handler() function

Definition and usage The restore_error_handler() function restores the previous error handler, which was changed by the set_error_handler() function.

This function always returns true.

is the inverse function of set_error_handler().

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