Editing Troubleshooting of PHP errors

PHP 問題的排除解決

== 檔案操作有關 ==
可否讀取或寫入：例如 imagejpeg($canvas, $filename, 100); 沒有顯示錯誤訊息，則需要
* 檢查檔案是否存在 [http://tw2.php.net/file_exists file_exists]
* 檢查暫存目錄是否可以寫入 [http://stackoverflow.com/questions/1520956/php-way-to-find-the-web-servers-temp-path upload - PHP way to find the web server's temp path? - Stack Overflow]
* 檢查該檔案所在該目錄是否已經建立，若未建立則需要建立 [http://php.net/manual/en/function.mkdir.php mkdir]，並設定可以寫入。如果是巢狀的多層目錄，則需要啟用 $recursive <ref>[http://stackoverflow.com/questions/2303372/create-a-folder-if-it-doesnt-already-exist php - Create a folder if it doesn't already exist - Stack Overflow]  code snippet: <nowiki>mkdir('path/to/directory', 0755, true);</nowiki> </ref>
* 檢查該檔案是否可以寫入 [http://php.net/manual/en/function.is-writable.php is_writable]

== 使用者操作/使用者輸入的內容 ==
使用者輸入內容，內容可能是
* 空值
* 包含特殊符號 ex: 單引號 ', 雙引號 ",  > < <== 對策: [http://www.php.net/manual/en/function.htmlentities.php PHP: htmlentities - Manual]
* 包含換行符號
* 內容的前後有空白 <== 對策: [http://php.net/manual/en/function.trim.php PHP: trim] 或 jQuery [http://api.jquery.com/jQuery.trim/ $.trim('string')]
* 超出預期的內容長度
* 重複的內容 ex: Excel 欄位重複
* (可勾選多個項目的狀況下) 指勾選了單一項目或者沒有勾選項目，就送出(submit)表格

使用者操作
* 重複點選按鈕
* 在輸入框按 {{kbd | key=Enter}}

== 操作順序 ==
* 使用者的操作順序，可能不按照功能設計的順序
* 沒有選取任何項目，就提交(submit)或操作表格

== 錯誤訊息 ==
=== 執行PHP時顯示原始碼的錯誤 ===
* 確認伺服器是否能執行 PHP。驗證: [http://php.net/manual/en/function.phpinfo.php phpinfo]/ [http://www.commandlinefu.com/commands/view/818/phpinfo-from-the-command-line phpinfo from the command line | commandlinefu.com]
* 如果 PHP 使用 short tag語法撰寫，則 php.ini 檔案 需要開啟 short_open_tag = Off -> On

=== 錯誤訊息: ERROR: 00000:: ===
* 原因: 想要刪除的資料不在 MySQL 資料庫內，進行刪除時，會發生的錯誤。
* 解決方法: 先檢查該資料是否存在，再進行刪除。

=== 錯誤訊息: phpinfo() has been disabled ===
<pre>
PHP Warning:  phpinfo() has been disabled for security reasons in /path/to/phpinfo.php on line xx
</pre>
* 原因: 網管關閉使用 phpinfo

替代解決方法: 使用 console command
* {{kbd | key = <nowiki>/path/to/bin/php -i | grep "變數名稱"</nowiki>}} for {{linux}}
* {{kbd | key = <nowiki>/path/to/bin/php -m</nowiki>}} 列出載入的模組<ref>[http://php.net/manual/en/function.extension-loaded.php PHP: extension_loaded - Manual]</ref>

=== 錯誤訊息: PHP syntax error “unexpected $end” ===
解決方法
* 檢查括弧是否封閉: 使用 [http://notepad-plus-plus.org/ Notepad++]{{kbd | key=ctrl}} + {{kbd | key=b}} 檢查括弧是否封閉 或 使用 [http://www.sublimetext.com/ Sublime Text]{{kbd | key=ctrl}} + {{kbd | key=m}} 檢查括弧是否封閉
* <nowiki><?php</nowiki> 是否簡寫為 shorttag <nowiki><?</nowiki>

=== 錯誤訊息: Invalid address: SMTP -> ERROR: Failed to connect to server: Permission denied (13) SMTP Error: Could not connect to SMTP host. Mailer Error: SMTP Error: Could not connect to SMTP host. ===
解決方法
* 檢查 PHP 模組是否安裝 OpenSSL {{kbd | key =<nowiki> php -r "phpinfo();" | grep -i "OpenSSL support"</nowiki> }} 或 {{kbd | key =<nowiki> php -i | grep -i OpenSSL</nowiki> }} for {{Linux}}
預期結果：
<pre>
OpenSSL support => enabled
</pre>
* 是否可以連線到 SMTP 主機{{kbd | key =<nowiki>nslookup smtp.gmail.com</nowiki> }} 或 {{kbd | key =<nowiki>telnet smtp.gmail.com port</nowiki> }} (例子中以 gmail 作為 smtp 伺服器)
預期結果：
<pre>
Trying 74.125.129.109...
Connected to smtp.gmail.com.
Escape character is '^]'.
^] //註：輸入 ctrl + ] 兩個按鍵
telnet> quit
Connection closed.
</pre>

非預期結果：請調整防火牆設定
<pre>
Trying x.x.x.x...
telnet: connect to address x.x.x.x: Connection refused
</pre>

* SELinux設定 [http://www.lahory.com/phpmailer-smtp-error-failed-to-connect-to-server-permission-denied-13/ PHPMailer SMTP -> ERROR: Failed to connect to server: Permission denied (13) | Lahory]

預期結果：
<pre>
# getsebool httpd_can_sendmail
httpd_can_sendmail --> on
# getsebool httpd_can_network_connect
httpd_can_network_connect --> on
</pre>

非預期結果：
<pre>
# getsebool httpd_can_sendmail
httpd_can_sendmail --> off
# getsebool httpd_can_network_connect
httpd_can_network_connect --> off
</pre>

需要輸入指令：
<pre>
# setsebool -P httpd_can_sendmail 1
# setsebool -P httpd_can_network_connect 1
</pre>

== unified coding style ==
variable: $var
* PHP: starts with dollar symbol $var<ref>[http://www.php.net/manual/en/language.variables.basics.php PHP: Basics - Manual]</ref>
* javascript: the first character can be a letter or _ or $, and the other characters can be letters or _ or $ or numbers.<ref>, and the other characters can be letters or _ or $ or numbers.</ref>

== troubleshooting steps of function ==
simply the question
* Is the [http://php.net/manual/en/function.function-exists.php function_exists]? If not, looking for the alternative functions.
* Was the function really executed? Maybe using the __LINE__ to examin the logic.
* Disable the logical judgement and just print text
* Check the if-else condition was satisfied or not cf: [http://www.leepoint.net/notes-java/data/strings/12stringcomparison.html Java: String Comparison] It's logical (compiler will not show the warning) but wrong.

== references ==
<references/>

[[Category:PHP]] [[Category:Programming]] [[Category:Linux]]