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Created by jinx on April 29, 2011 15:39:05
Last update: April 29, 2011 15:39:05
When you call a non-existing function in PHP, it dies immediately with "PHP Fatal error: Call to undefined function". The error handler is not bothered even when you have one in place:
<?php
set_error_handler(function($errno, $e...
It's safer to use call_user_func :
<?php
set_error_handler(function($errno...
Created by jinx on April 29, 2011 15:26:44
Last update: April 29, 2011 15:27:53
The PHP function set_error_handle sets a user defined error handler function. The example below uses a global variable to alter the execution path after error occurs:
<?php
$continue = true;
set_error_ha...
Output:
[Error Handler]
errno: 2
errstr: Division by...
Created by jinx on April 29, 2011 15:03:10
Last update: April 29, 2011 15:04:02
The PHP function is_callable verifies that a variable can be invoked as a function.
Example:
<?php
define('F', 'f');
function...
Output:
var_dump: string(1) "f"
is_callable: 1
Calla...
Created by jinx on April 28, 2011 20:52:45
Last update: April 29, 2011 13:27:31
This is normally a syntax error just before some variable. Try some of these:
Missing operator before a variable:
<?php
$a = 'ab';
echo('Missing conca...
Missing semicolon at end of line:
<?php
echo('Missing semicolon at end of lin...
Missing ( and ) in for loop:
<?php
foreach $a as $i {
echo "$i\n";
...
Missing keyword before class variable:
<?php
class A {
// should be var $a;
...
Created by Dr. Xi on April 26, 2011 20:12:01
Last update: April 28, 2011 15:28:12
An XML schema is a definition of XML files, in XML. It plays the same role as old-time DTDs. Overall, an XML schema file looks like this:
<schema attributeFormDefault = (qualified | u... The attribute meanings: targetNamespace : The name space targeted by the current schema definition. It can be any URI. id and version : For user convenience, the W3C spec defines no semantics for them. xml:lang : Natural language identifier defined by RFC 3306 . attributeFormDefault and elementFormDefault : Set default values for the form attribute for attribute and element declarations. blockDefault and finalDefault : Set default values for the block and final attributes for attribute and element declarations. The W3C defined some built-in datatypes . Examples of primitive datatypes are: string ,...
Created by Dr. Xi on April 27, 2011 11:57:36
Last update: April 27, 2011 11:58:35
This is a sample struts-config.xml file for Struts 1.x .
<?xml version="1.0" encoding="UTF-8"?>
<!DO...
Created by jinx on April 26, 2011 21:52:10
Last update: April 26, 2011 21:52:10
PHP offers several ways to check the class type of an object instance at runtime: instanceof operator, is_a function, get_class function.
Example:
<?php
class A {
}
class B {
}
...
Created by jinx on April 25, 2011 12:43:40
Last update: April 25, 2011 12:43:40
Use the PHP function method_exists to check if the class or object has a certain method. It returns TRUE if the method exists (even when the value of the property is NULL), FALSE if the method does not exist.
Example:
<?php
class A {
var $p = 'A property';
...
Outputs:
Class A has method f1: bool(true)
Object $a has...
Also note that C++-like method overloading does not exist in PHP. Thus there's no ambiguity about which version of the method exists, i.e., with no argument, with one argument... etc. The following code generates Fatal error:
<?php
class A {
var $p = 'A property';
...
Created by jinx on April 25, 2011 11:50:09
Last update: April 25, 2011 11:51:53
Use the PHP function property_exists to check if the class or object has a certain property. It returns TRUE if the property exists (even when the value of the property is NULL), FALSE if the property does not exist, or NULL in case of an error.
Example:
<?php
class A {
var $p = 'A property';
...
Outputs:
Class A has property $p: bool(false)
Class A ha...
Created by freyo on April 20, 2011 12:26:08
Last update: April 20, 2011 12:26:08
When you create a new key with Java keytool , it wraps the public key in a self signed certificate. You can generate a certificate signing request with the keytool -certreq command. After a certificate authority (CA) signs the certificate request, you can import the certificate received (a .crt file) back into the key store. Instead of using a CA, you can sign the certificate request with another key (with openssl, for example). If the certificate is not signed by a CA, you'll receive an error:
$ keytool -import -alias android-root -file androi... To fix the problem, import the certificate of the signer: $ keytool -import -trustcacerts -file openssl.crt ... Import the certificate again (alias is the alias of the private key whose certificate was...
