learn how to print backtraces in php

1 files changed, 61 insertions, 0 deletions

diff --git a/error_log-to-currdir.php b/error_log-to-currdir.php
new file mode 100644
index 0000000..32d1de4
--- /dev/null
+++ b/error_log-to-currdir.php
@@ -0,0 +1,61 @@
+<?php
+
+error_reporting(E_ALL | E_STRICT);
+ini_set('display_errors', 1);
+ini_set('log_errors', 1);
+ini_set('log_errors_max_len', 0); /* unlimited */
+ini_set('error_log', './php_errors.log');
+
+register_shutdown_function(function() {
+    // error_log func not available here due to fatal php shutdown
+    //error_log(print_r(debug_backtrace(), TRUE));
+
+});
+
+function a($arg) {
+    b('beta');
+}
+
+function b($arg) {
+    c('charlie');
+}
+
+function c($arg) {
+    d('delta');
+}
+
+function d($arg) {
+    /* calling error_log in register_shutdown_function is too late, however var_dump still works there, in case of error
+     * in real code insert the line below above the line causing trouble
+     */
+    error_log(print_r(debug_backtrace(), TRUE));
+
+    /* nicer output */
+    $e = new Exception;
+    error_log($e->getTraceAsString());
+
+    /* print to screen in simple format */
+    print mydebug_bt();
+
+    trigger_error("user triggered error", E_USER_ERROR);
+}
+
+error_log('calling a()', 0, './php_errors.log');
+a('alpha');
+
+/* simplify and beatify the output of a dump of debug_backtrace() */
+function mydebug_bt() {
+    $stack = '';
+    $i = 1;
+    $trace = debug_backtrace();
+    unset($trace[0]); // remove call to this function from stack trace
+    foreach($trace as $node) {
+        $stack .= "#$i ".$node['file'] ."(" .$node['line']."): ";
+        if(isset($node['class'])) {
+            $stack .= $node['class'] . "->";
+        }
+        $stack .= $node['function'] . "()" . PHP_EOL;
+        $i++;
+    }
+    return $stack;
+}