Error handling is an important part when creating scripts and web applications. If your code lacks error detection coding, the program will look unprofessional and open the door to security risks.
Basic error handling: Using the die() function
The first example shows a simple script that opens a text file : (Recommended learning: PHP Video Tutorial)
<?php $file=fopen("welcome.txt","r"); ?>
If the file does not exist, you will get an error similar to this:
Warning: fopen(welcome.txt) [function.fopen]: failed to open stream: No such file or directory in C:\webfolder\test.php on line 2
In order to avoid users getting errors similar to the above message, we check whether the file exists before accessing it:
<?php if(!file_exists("welcome.txt")) { die("File not found"); } else { $file=fopen("welcome.txt","r"); } ?>
Now, if the file does not exist, you will get an error message like this:
File not found
Compared to the previous code, the above The code is more efficient because it uses a simple error handling mechanism that terminates the script after an error.
However, simply terminating the script is not always appropriate. Let's examine alternative PHP functions for handling errors.
Create a custom error handler
Creating a custom error handler is very simple. We simply created a dedicated function that can be called when an error occurs in PHP.
The function must be able to handle at least two parameters (error level and error message), but can accept up to five parameters (optional: file, line-number and error context):
error_function(error_level,error_message, error_file,error_line,error_context)
Trigger Error
It is useful to trigger an error when the user inputs invalid data in the script. In PHP, this task is accomplished by trigger_error().
Error Logging
By default, PHP sends error logs to the server's error logging system or file according to the error_log configuration in php.ini. By using the error_log() function, you can send error records to a specified file or remote destination.
Emailing yourself an error message is a good way to get notified of a specified error.
The above is the detailed content of How to detect php errors. For more information, please follow other related articles on the PHP Chinese website!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。


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