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><H1
><A
NAME="function.substr"
></A
>substr</H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN228602"
></A
><P
> (PHP 3, PHP 4, PHP 5)</P
>substr -- Return part of a string</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN228605"
></A
><H2
>Description</H2
>string <B
CLASS="methodname"
>substr</B
> ( string string, int start [, int length] )<BR
></BR
><P
> <B
CLASS="function"
>substr()</B
> returns the portion of <CODE
CLASS="parameter"
>string</CODE
>
specified by the <CODE
CLASS="parameter"
>start</CODE
> and
<CODE
CLASS="parameter"
>length</CODE
> parameters.
</P
><P
> If <CODE
CLASS="parameter"
>start</CODE
> is non-negative, the returned string
will start at the <CODE
CLASS="parameter"
>start</CODE
>'th position in
<CODE
CLASS="parameter"
>string</CODE
>, counting from zero. For instance,
in the string '<TT
CLASS="literal"
>abcdef</TT
>', the character at
position <TT
CLASS="literal"
>0</TT
> is '<TT
CLASS="literal"
>a</TT
>', the
character at position <TT
CLASS="literal"
>2</TT
> is
'<TT
CLASS="literal"
>c</TT
>', and so forth.
</P
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><TD
><DIV
CLASS="example"
><A
NAME="AEN228633"
></A
><P
><B
>例 1. Basic <B
CLASS="function"
>substr()</B
> usage</B
></P
><TABLE
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><TR
><TD
><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">echo </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">'abcdef'</font><font color="#007700">, </font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// bcdef<br /></font><font color="#007700">echo </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">'abcdef'</font><font color="#007700">, </font><font color="#0000BB">1</font><font color="#007700">, </font><font color="#0000BB">3</font><font color="#007700">); </font><font color="#FF8000">// bcd<br /></font><font color="#007700">echo </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">'abcdef'</font><font color="#007700">, </font><font color="#0000BB">0</font><font color="#007700">, </font><font color="#0000BB">4</font><font color="#007700">); </font><font color="#FF8000">// abcd<br /></font><font color="#007700">echo </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">'abcdef'</font><font color="#007700">, </font><font color="#0000BB">0</font><font color="#007700">, </font><font color="#0000BB">8</font><font color="#007700">); </font><font color="#FF8000">// abcdef<br /></font><font color="#007700">echo </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">'abcdef'</font><font color="#007700">, -</font><font color="#0000BB">1</font><font color="#007700">, </font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// f<br /><br />// Accessing single characters in a string<br />// can also be achived using "curly braces"<br /></font><font color="#0000BB">$string </font><font color="#007700">= </font><font color="#DD0000">'abcdef'</font><font color="#007700">;<br />echo </font><font color="#0000BB">$string</font><font color="#007700">{</font><font color="#0000BB">0</font><font color="#007700">}; </font><font color="#FF8000">// a<br /></font><font color="#007700">echo </font><font color="#0000BB">$string</font><font color="#007700">{</font><font color="#0000BB">3</font><font color="#007700">}; </font><font color="#FF8000">// d<br /></font><font color="#007700">echo </font><font color="#0000BB">$string</font><font color="#007700">{</font><font color="#0000BB">strlen</font><font color="#007700">(</font><font color="#0000BB">$string</font><font color="#007700">)-</font><font color="#0000BB">1</font><font color="#007700">}; </font><font color="#FF8000">// f<br /><br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
><P
> If <CODE
CLASS="parameter"
>start</CODE
> is negative, the returned string
will start at the <CODE
CLASS="parameter"
>start</CODE
>'th character
from the end of <CODE
CLASS="parameter"
>string</CODE
>.
</P
><TABLE
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><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN228641"
></A
><P
><B
>例 2. Using a negative <CODE
CLASS="parameter"
>start</CODE
></B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
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><TR
><TD
><code><font color="#000000">
<font color="#0000BB"><?php<br />$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, -</font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// returns "f"<br /></font><font color="#0000BB">$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, -</font><font color="#0000BB">2</font><font color="#007700">); </font><font color="#FF8000">// returns "ef"<br /></font><font color="#0000BB">$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, -</font><font color="#0000BB">3</font><font color="#007700">, </font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// returns "d"<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
><P
> If <CODE
CLASS="parameter"
>length</CODE
> is given and is positive, the string
returned will contain at most <CODE
CLASS="parameter"
>length</CODE
> characters
beginning from <CODE
CLASS="parameter"
>start</CODE
> (depending on the length of
<CODE
CLASS="parameter"
>string</CODE
>). If <CODE
CLASS="parameter"
>string</CODE
> is less
than or equal to <CODE
CLASS="parameter"
>start</CODE
> characters long, <TT
CLASS="constant"
><B
>FALSE</B
></TT
>
will be returned.
</P
><P
> If <CODE
CLASS="parameter"
>length</CODE
> is given and is negative, then that many
characters will be omitted from the end of <CODE
CLASS="parameter"
>string</CODE
>
(after the start position has been calculated when a
<CODE
CLASS="parameter"
>start</CODE
> is negative). If
<CODE
CLASS="parameter"
>start</CODE
> denotes a position beyond this truncation,
an empty string will be returned.
</P
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><DIV
CLASS="example"
><A
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></A
><P
><B
>例 3. Using a negative <CODE
CLASS="parameter"
>length</CODE
></B
></P
><TABLE
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><TR
><TD
><code><font color="#000000">
<font color="#0000BB"><?php<br />$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, </font><font color="#0000BB">0</font><font color="#007700">, -</font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// returns "abcde"<br /></font><font color="#0000BB">$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, </font><font color="#0000BB">2</font><font color="#007700">, -</font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// returns "cde"<br /></font><font color="#0000BB">$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, </font><font color="#0000BB">4</font><font color="#007700">, -</font><font color="#0000BB">4</font><font color="#007700">); </font><font color="#FF8000">// returns ""<br /></font><font color="#0000BB">$rest </font><font color="#007700">= </font><font color="#0000BB">substr</font><font color="#007700">(</font><font color="#DD0000">"abcdef"</font><font color="#007700">, -</font><font color="#0000BB">3</font><font color="#007700">, -</font><font color="#0000BB">1</font><font color="#007700">); </font><font color="#FF8000">// returns "de"<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
><P
> See also <A
HREF="function.strrchr.html"
><B
CLASS="function"
>strrchr()</B
></A
>,
<A
HREF="function.substr-replace.html"
><B
CLASS="function"
>substr_replace()</B
></A
>,
<A
HREF="function.preg-match.html"
><B
CLASS="function"
>preg_match()</B
></A
>,
<A
HREF="function.trim.html"
><B
CLASS="function"
>trim()</B
></A
>,
<A
HREF="function.mb-substr.html"
><B
CLASS="function"
>mb_substr()</B
></A
> and
<A
HREF="function.wordwrap.html"
><B
CLASS="function"
>wordwrap()</B
></A
>.
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