(4) PHP Object-Oriented Theory 4---Exception and Error Handling

one. Exception handling:
1. PHP exception examples:

<?php
//运行无结果。
$a = null;
try{
    $a = 5 / 0 ;
    echo $a,PHP_EOL;
}catch(exception $e){
    $e->getMessage();
    $a = -1;
}
echo $a;

2. Detailed exception examples:

<?php
header("Content-type: text/html; charset=utf-8");

class emailException extends exception{

}
class pwdException extends exception{
    function __toString(){
        return "<div class =\"error\">Exception($this->getCode()):
        {$this->getMessage()}
        in File:($this->getFile()) on Line:{$this->getLine()}</div>";
    }
}

function reg($reginfo =null){
    if (empty($reginfo) || isset($reginfo)){
        throw new Exception("参数非法");
    }
    if (empty($reginfo['email'])){
        throw new emailException("邮件为空");
    }
    if ($reginfo['pwd'] != $reginfo['repwd']){
        throw new pwdException("两次密码不一致");
    }
    echo "注册成功";
}
/*
 * 这个代码无法执行，抽空找原因
 */

try{
    reg(array('email' => 'waitfox@qq.com','pwd'=>123456,'repwd'=>12345678));
}catch (emailException $ee){
    echo $ee->getMessage();
}catch (pwdException $ep){
    echo $ep;
    echo PHP_EOL,"特殊处理";
}catch (Exception $e){
    echo $e->getTraceAsString();
    echo PHP_EOL,"其他情况统一处理";
}

3. Scenarios where exception handling is used:
a. Pessimistic predictions about the program
b. Program needs and business concerns
c. Language-level robustness requirements: catch exceptions and make corresponding remedies
3. Facing exceptions: handling exceptions needs to be handled in reasonable scenarios
2. PHP error level:
1.PHP error level:
a.deprecated: the lowest level. ‘Not recommended, not recommended’
b.notice: Improper grammar. For example, using a variable without defining it
c.warning: function parameters do not match
d.fetal error: directly leads to the termination of the PHP process, and the following code will no longer be executed.
e.prase error: This error will be reported during the syntax checking phase. The PHP manual defines a total of 16 levels of errors.
2. Example:

<?php
//php5.6，据说可以演示错误，但我出现了正确结果……
$date = &#39;2012-12-20&#39;;
if (ereg("([0-9]{4})-([0-9]{1,2})-([0-9]{1,2})",$date,$regs)){
    echo "$regs[3].$regs[2].$regs[1]";
}else{
    echo "Invaild date format:$date";
}

if ($i>5){
    echo "$i没有初始化啊",PHP_EOL;
}

$a = array('o'=>2,4,6,8);
echo $a[o];
$result = array_sum($a,3);
echo fun();
echo "错误了…… 能继续吗？";

4. PHP error handling mechanism:

<?php
function customerError($errno,$errstr,$errfile,$errline){
    echo "<b>错误代码:</b>[${errno}],文件{$errstr}\r\n";
    echo "错误所在的代码行:{$errline}文件{$errfile}\r\n";
    echo "PHP版本",PHP_VERSION,"(",PHP_OS,")\r\n";
}

set_error_handler("customeError",E_ALL|E_STRICT);
$a = array('o'=>2,4,6,8);
echo $a['o'];

//此问题亦无答案。没有报错

3. Summary of PHP object-oriented:
PHP object-oriented knowledge points: magic methods, interfaces, polymorphism, class reuse, reflection, exception mechanism.
PHP also introduces some functional programming concepts.

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The above has introduced (4) PHP object-oriented theory 4---exception and error handling, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.