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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.strspn" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>strspn</refname>
<refpurpose>
Finds the length of the initial segment of a string consisting
entirely of characters contained within a given mask
</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>int</type><methodname>strspn</methodname>
<methodparam><type>string</type><parameter>string</parameter></methodparam>
<methodparam><type>string</type><parameter>characters</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>offset</parameter><initializer>0</initializer></methodparam>
<methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>length</parameter><initializer>&null;</initializer></methodparam>
</methodsynopsis>
<para>
Finds the length of the initial segment of <parameter>string</parameter>
that contains <emphasis>only</emphasis> characters from <parameter>characters</parameter>.
</para>
<para>
If <parameter>offset</parameter> and <parameter>length</parameter>
are omitted, then all of <parameter>string</parameter> will be
examined. If they are included, then the effect will be the same as
calling <literal>strspn(substr($string, $offset, $length),
$characters)</literal> (see <xref linkend="function.substr"/>
for more information).
</para>
<para>
The line of code:
<informalexample>
<programlisting role="php">
<![CDATA[
<?php
$var = strspn("42 is the answer to the 128th question.", "1234567890");
?>
]]>
</programlisting>
</informalexample>
will assign <literal>2</literal> to <varname>$var</varname>,
because the string "42" is the initial segment
of <parameter>string</parameter> that consists only of characters
contained within "1234567890".
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>string</parameter></term>
<listitem>
<para>
The string to examine.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>characters</parameter></term>
<listitem>
<para>
The list of allowable characters.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>offset</parameter></term>
<listitem>
<para>
The position in <parameter>string</parameter> to
start searching.
</para>
<para>
If <parameter>offset</parameter> is given and is non-negative,
then <function>strspn</function> will begin
examining <parameter>string</parameter> at
the <parameter>offset</parameter>'th position. For instance, in
the string '<literal>abcdef</literal>', the character at
position <literal>0</literal> is '<literal>a</literal>', the
character at position <literal>2</literal> is
'<literal>c</literal>', and so forth.
</para>
<para>
If <parameter>offset</parameter> is given and is negative,
then <function>strspn</function> will begin
examining <parameter>string</parameter> at
the <parameter>offset</parameter>'th position from the end
of <parameter>string</parameter>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>length</parameter></term>
<listitem>
<para>
The length of the segment from <parameter>string</parameter>
to examine.
</para>
<para>
If <parameter>length</parameter> is given and is non-negative,
then <parameter>string</parameter> will be examined
for <parameter>length</parameter> characters after the starting
position.
</para>
<para>
If <parameter>length</parameter> is given and is negative,
then <parameter>string</parameter> will be examined from the
starting position up to <parameter>length</parameter>
characters from the end of <parameter>string</parameter>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns the length of the initial segment of <parameter>string</parameter>
which consists entirely of characters in <parameter>characters</parameter>.
</para>
<note>
<para>
When a <parameter>offset</parameter> parameter is set, the returned length
is counted starting from this position, not from the beginning of
<parameter>string</parameter>.
</para>
</note>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>8.0.0</entry>
<entry>
<parameter>length</parameter> is nullable now.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>strspn</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// subject does not start with any characters from mask
var_dump(strspn("foo", "o"));
// examine two characters from subject starting at offset 1
var_dump(strspn("foo", "o", 1, 2));
// examine one character from subject starting at offset 1
var_dump(strspn("foo", "o", 1, 1));
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
int(0)
int(2)
int(1)
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
¬e.bin-safe;
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>strcspn</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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