Several common mistakes and solutions for PHP beginners

This article shares several common mistakes and solutions for PHP beginners, hoping to help those who are just learning PHP.

Error 1: Parse error: syntax error, unexpected...

This error is that the PHP parser encountered a syntax error during parsing, which is literally translated as: parsing Error: Syntax error, unexpected...

Cause and solution:

Wrong syntax format. For example: every statement should end with an English semicolon. If the semicolon is not written or typed in a Chinese semicolon, such an error will be reported. This can be avoided as long as we pay attention to the syntax format when writing code.

Error 2: Fatal error: Uncaught Error: Call to undefined function...

This error indicates that the code encountered a fatal error during execution, which is literally translated as: Uncaught error: An undefined function was called

Cause and solution:

An undefined function was called. When encountering this kind of error, we first need to check the error message, locate the line where the error code is located, and check whether the function name is spelled incorrectly or whether the custom function is really not defined.

Solution:

Error 3: Notice: Array to string conversion in...

This error is very easy for beginners to encounter A problem is just an error message and does not affect the execution of the entire code. Literal translation: The array is converted into a string at line...

Solution:

This error is generally caused by an array being output after echo, or the array is used as a string Caused when performing splicing operations. (php is a weakly typed language and will automatically convert data types according to environmental needs during operation)

We only need to find the line of code prompted, process the array in advance, and then perform string operations.

Error four: Parse error: syntax error, unexpected '1' (T_LNUMBER), expecting variable

Cause and solution:

Locate For the code that reported the error, check whether the variables or functions are named correctly.

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Error 5: Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean given...

The error is literally translated as: Warning: The mysqli_fetch_assoc function expected parameter 1 to be the result set of mysqli, but a Boolean value was given. This error is a warning error and does not affect program execution.

This error usually occurs when the database reads the result set data. For example, when we write a SQL statement to read data from the database, we should return the result set and then read the data into the result set. However, the result set is a Boolean value, so it is very likely that the SQL statement was written incorrectly, causing an execution error, and the result set becomes the execution result false.

Solution:

Check the SQL statement carefully and confirm that there is no problem before submitting it to the server for execution.

Error six: Notice: Undefined variable:...

The literal translation of this error is: Tip: Undefined variable a

Cause and solution:

This error generally occurs when undefined variables are used. When encountering this kind of problem, we only need to double-check whether the definition or spelling of the variable is correct.

Error 7: Notice: Undefined index: username in...

The literal translation of this error is: Tip: Undefined index: username

Cause and solution:

This error generally occurs when undefined array elements are used. Associative arrays in PHP can use key names to access values. At the same time, they are also prompted by indexing the array, so many beginners will misunderstand.

We only need to carefully check whether the array key name is spelled incorrectly or is undefined.

Error 8: Garbled characters

Cause and solution:

The character set when php generates html code is different from the character set displayed by the browser by default caused. We can add a response header at the top of the php script to declare the character set. For example: [header('Content-Type: text/html; charset=utf-8')].

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