$ rpm -q php curl libcurl
php-5.3.8-2.el5.remi
curl-7.21.7-4.el5.remi
libcurl-7.21.7-4.el5.remi

$ ldd /usr/lib*/php/modules/curl.so
    libcurl.so.4 => /usr/lib64/libcurl.so.4 (0x00002b6a1ea0c000)
    libc.so.6 => /lib64/libc.so.6 (0x00002b6a1ec66000)
    libidn.so.11 => /usr/lib64/libidn.so.11 (0x00002b6a1efbd000)
    libldap-2.3.so.0 => /usr/lib64/libldap-2.3.so.0 (0x00002b6a1f1ef000)
    librt.so.1 => /lib64/librt.so.1 (0x00002b6a1f429000)
    libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2 (0x00002b6a1f632000)
    libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x00002b6a1f861000)
    libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3 (0x00002b6a1faf6000)
    libcom_err.so.2 => /lib64/libcom_err.so.2 (0x00002b6a1fd1b000)
    libz.so.1 => /usr/lib64/libz.so.1 (0x00002b6a1ff1e000)
    libssl3.so => /usr/lib64/libssl3.so (0x00002b6a20132000)
    libsmime3.so => /usr/lib64/libsmime3.so (0x00002b6a20368000)
    libnss3.so => /usr/lib64/libnss3.so (0x00002b6a20593000)
    libnssutil3.so => /usr/lib64/libnssutil3.so (0x00002b6a208c0000)
    libplds4.so => /usr/lib64/libplds4.so (0x00002b6a20ade000)
    libplc4.so => /usr/lib64/libplc4.so (0x00002b6a20ce2000)
    libnspr4.so => /usr/lib64/libnspr4.so (0x00002b6a20ee6000)
    libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b6a21121000)
    libdl.so.2 => /lib64/libdl.so.2 (0x00002b6a2133d000)
    libssh2.so.1 => /usr/lib64/libssh2.so.1 (0x00002b6a21541000)
    /lib64/ld-linux-x86-64.so.2 (0x0000003c71000000)
    liblber-2.3.so.0 => /usr/lib64/liblber-2.3.so.0 (0x00002b6a21764000)
    libresolv.so.2 => /lib64/libresolv.so.2 (0x00002b6a21973000)
    libsasl2.so.2 => /usr/lib64/libsasl2.so.2 (0x00002b6a21b88000)
    libssl.so.6 => /lib64/libssl.so.6 (0x00002b6a21da1000)
    libcrypto.so.6 => /lib64/libcrypto.so.6 (0x00002b6a21fee000)
    libkrb5support.so.0 => /usr/lib64/libkrb5support.so.0 (0x00002b6a2233f000)
    libkeyutils.so.1 => /lib64/libkeyutils.so.1 (0x00002b6a22547000)
    libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00002b6a2274a000)
    libselinux.so.1 => /lib64/libselinux.so.1 (0x00002b6a22982000)
    libsepol.so.1 => /lib64/libsepol.so.1 (0x00002b6a22b9b000)

$ php -m | grep curl
PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/curl.so' - /usr/lib64/libcurl.so.4: undefined symbol: ldap_init_fd in Unknown on line 0

$ php -i | grep -i curl
PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/curl.so' - /usr/lib64/libcurl.so.4: undefined symbol: ldap_init_fd in Unknown on line 0
Configure Command =>  './configure'  '--build=x86_64-redhat-linux-gnu' '--host=x86_64-redhat-linux-gnu' '--target=x86_64-redhat-linux-gnu' '--program-prefix=' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc' '--datadir=/usr/share' '--includedir=/usr/include' '--libdir=/usr/lib64' '--libexecdir=/usr/libexec' '--localstatedir=/var' '--sharedstatedir=/usr/com' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--cache-file=../config.cache' '--with-libdir=lib64' '--with-config-file-path=/etc' '--with-config-file-scan-dir=/etc/php.d' '--disable-debug' '--with-pic' '--disable-rpath' '--without-pear' '--with-bz2' '--with-exec-dir=/usr/bin' '--with-freetype-dir=/usr' '--with-png-dir=/usr' '--with-xpm-dir=/usr' '--enable-gd-native-ttf' '--with-t1lib=/usr' '--without-gdbm' '--with-gettext' '--with-gmp' '--with-iconv' '--with-jpeg-dir=/usr' '--with-openssl' '--with-zlib' '--with-layout=GNU' '--enable-exif' '--enable-ftp' '--enable-magic-quotes' '--enable-sockets' '--with-kerberos' '--enable-ucd-snmp-hack' '--enable-shmop' '--enable-calendar' '--with-libxml-dir=/usr' '--enable-xml' '--with-system-tzdata' '--with-mhash' '--enable-force-cgi-redirect' '--enable-pcntl' '--with-imap=shared' '--with-imap-ssl' '--enable-mbstring=shared' '--enable-mbregex' '--with-gd=shared' '--enable-bcmath=shared' '--enable-dba=shared' '--with-db4=/usr' '--with-xmlrpc=shared' '--with-ldap=shared' '--with-ldap-sasl' '--with-mysql=shared,/usr' '--with-mysqli=shared,/usr/lib64/mysql/mysql_config' '--with-oci8=shared,instantclient,/usr/lib64/oracle/11.2/client64/lib,11.2' '--with-pdo-oci=shared,instantclient,/usr,11.2' '--with-interbase=shared,/usr/lib64/firebird' '--with-pdo-firebird=shared,/usr/lib64/firebird' '--enable-dom=shared' '--with-pgsql=shared' '--enable-wddx=shared' '--with-snmp=shared,/usr' '--enable-soap=shared' '--with-xsl=shared,/usr' '--enable-xmlreader=shared' '--enable-xmlwriter=shared' '--with-curl=shared,/usr' '--enable-fastcgi' '--enable-pdo=shared' '--with-pdo-odbc=shared,unixODBC,/usr' '--with-pdo-mysql=shared,/usr/lib64/mysql/mysql_config' '--with-pdo-pgsql=shared,/usr' '--with-pdo-sqlite=shared,/usr' '--with-pdo-dblib=shared,/usr' '--without-sqlite3' '--with-sqlite=shared,/usr' '--enable-json=shared' '--enable-zip=shared' '--without-readline' '--with-libedit' '--with-pspell=shared' '--enable-phar=shared' '--with-mcrypt=shared,/usr' '--with-tidy=shared,/usr' '--with-mssql=shared,/usr' '--enable-sysvmsg=shared' '--enable-sysvshm=shared' '--enable-sysvsem=shared' '--enable-posix=shared' '--with-unixODBC=shared,/usr' '--enable-fileinfo=shared' '--enable-intl=shared' '--with-icu-dir=/usr' '--with-enchant=shared,/usr' '--with-recode=shared,/usr'
/etc/php.d/curl.ini,
libcurl => 7.15.5 => 7.15.5

$ ldd /usr/lib*/libcurl.so.4
    libidn.so.11 => /usr/lib64/libidn.so.11 (0x00002b0d99d08000)
    libldap-2.3.so.0 => /usr/lib64/libldap-2.3.so.0 (0x00002b0d99f39000)
    librt.so.1 => /lib64/librt.so.1 (0x00002b0d9a173000)
    libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2 (0x00002b0d9a37d000)
    libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x00002b0d9a5ab000)
    libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3 (0x00002b0d9a840000)
    libcom_err.so.2 => /lib64/libcom_err.so.2 (0x00002b0d9aa66000)
    libz.so.1 => /usr/lib64/libz.so.1 (0x00002b0d9ac68000)
    libssl3.so => /usr/lib64/libssl3.so (0x00002b0d9ae7c000)
    libsmime3.so => /usr/lib64/libsmime3.so (0x00002b0d9b0b3000)
    libnss3.so => /usr/lib64/libnss3.so (0x00002b0d9b2dd000)
    libnssutil3.so => /usr/lib64/libnssutil3.so (0x00002b0d9b60a000)
    libplds4.so => /usr/lib64/libplds4.so (0x00002b0d9b829000)
    libplc4.so => /usr/lib64/libplc4.so (0x00002b0d9ba2c000)
    libnspr4.so => /usr/lib64/libnspr4.so (0x00002b0d9bc30000)
    libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b0d9be6c000)
    libdl.so.2 => /lib64/libdl.so.2 (0x00002b0d9c087000)
    libssh2.so.1 => /usr/lib64/libssh2.so.1 (0x00002b0d9c28b000)
    libc.so.6 => /lib64/libc.so.6 (0x00002b0d9c4af000)
    liblber-2.3.so.0 => /usr/lib64/liblber-2.3.so.0 (0x00002b0d9c806000)
    libresolv.so.2 => /lib64/libresolv.so.2 (0x00002b0d9ca14000)
    libsasl2.so.2 => /usr/lib64/libsasl2.so.2 (0x00002b0d9cc2a000)
    libssl.so.6 => /lib64/libssl.so.6 (0x00002b0d9ce43000)
    libcrypto.so.6 => /lib64/libcrypto.so.6 (0x00002b0d9d08f000)
    /lib64/ld-linux-x86-64.so.2 (0x0000003c71000000)
    libkrb5support.so.0 => /usr/lib64/libkrb5support.so.0 (0x00002b0d9d3e1000)
    libkeyutils.so.1 => /lib64/libkeyutils.so.1 (0x00002b0d9d5e9000)
    libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00002b0d9d7ec000)
    libselinux.so.1 => /lib64/libselinux.so.1 (0x00002b0d9da24000)
    libsepol.so.1 => /lib64/libsepol.so.1 (0x00002b0d9dc3d000)

$ rpm -q openldap
openldap-2.3.43-12.el5_5.3

But shouldn't the dependencies in php-common or in libcurl be set to require that openldap version?

Anyway, thanks very much!