How to write php to let jq's ajax enter the error callback function

that is, after my php executes any code or outputs something, the ajax submitted by jquery on my web page can enter the error callback function, preferably the one with information

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Ajax jquery javascript php
Jun.19,2022

if you just want to enter the error callback function and the status code is 4xx, 5xx can 

  
 isn't it directly 500 if you write the wrong code

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MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e55a88-45352.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e55a88-45352.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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